多播路由是网络通信的核心技术之一，Linux内核通过精密的多层设计实现了高性能的IPv4多播路由功能。本文将深入剖析其核心实现机制，揭示其高效运转的秘密。
一、核心数据结构：路由系统的基石
1. 多播路由表（struct mr_table）
struct mr_table {struct list_head list;struct rhltable mfc_hash; // MFC哈希表struct list_head mfc_cache_list; struct list_head mfc_unres_queue; // 未解析队列struct vif_device vif_table[MAXVIFS]; // 虚拟接口表int maxvif; // 当前最大VIF索引atomic_t cache_resolve_queue_len; // 未解析队列长度struct timer_list ipmr_expire_timer; // 超时定时器
};路由表通过双结构存储策略实现高效检索：哈希表用于快速查找，链表用于顺序遍历。未解析队列则临时存放等待路由决策的数据包。
2. 虚拟接口（struct vif_device）
struct vif_device {struct net_device *dev; // 关联的网络设备unsigned long bytes_in, bytes_out; // 流量统计unsigned long pkt_in, pkt_out;__be32 local, remote; // 隧道端点地址int flags; // 类型标记
};支持三种接口类型：
物理接口：直接绑定网络设备
隧道接口（
VIFF_TUNNEL）：用于跨网络转发注册接口（
VIFF_REGISTER）：与用户态守护进程通信
3. 多播转发缓存（struct mfc_cache）
struct mfc_cache {struct mfc_common _c;__be32 mfc_origin; // 源地址__be32 mfc_mcastgrp; // 组地址struct mfc_cache_cmp_arg cmparg; // 哈希比较参数
};关键字段res.ttls[MAXVIFS]存储每个出口的TTL阈值，实现精细化的出口控制。
二、数据包转发流程：速度与精确的平衡
转发路径（ip_mr_forward）
graph TDA[数据包到达] --> B{匹配MFC?}B -->|是| C[校验输入接口]B -->|否| D[加入未解析队列]C --> E[遍历所有出口]E --> F{TTL有效?}F -->|是| G[克隆并发送]F -->|否| H[跳过接口]G --> I[更新统计信息]关键优化点：
快速克隆机制：对每个有效出口只克隆包头，避免数据复制
if (psend != -1) {struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);ipmr_queue_xmit(..., skb2, ...); }智能TTL管理：跳过TTL不足的接口，减少无效操作
统计原子更新：无锁更新计数器确保高性能
三、控制平面：动态路由管理
1. MFC生命周期管理
动态学习：通过PIM/IGMP消息自动创建条目
静态配置：Netlink命令手动添加
ip mroute add 192.168.1.100 224.0.0.1 dev eth0
超时清理：10秒未解析自动丢弃（可配置）
#define MFC_UNRES_TIMEOUT (10*HZ)
2. 用户态协同机制
内核通过原始套接字与mrouted/pimd交互：
static void igmpmsg_netlink_event(struct mr_table *mrt, struct sk_buff *pkt)
{// 构造IGMPMSG_NOCACHE消息// 通过NETLINK发送到用户态
}实现实时路由更新和未解析包通知。
四、协议支持：灵活的处理框架
1. PIM协议处理
// PIMv2处理函数
static int pim_rcv(struct sk_buff *skb)
{if (pim->type != ((PIM_VERSION<<4)|PIM_TYPE_REGISTER))goto drop;// 验证校验和// 转发到注册接口
}支持PIM-SM/PIM-DM关键特性，包括注册停止机制。
2. IGMP代理
static int ipmr_cache_report(struct mr_table *mrt,struct sk_buff *pkt, vifi_t vifi, int assert)
{// 构造IGMPMSG_WHOLEPKT消息// 发送到用户态套接字
}实现组播组成员关系的跨网络传播。
五、创新设计：性能与扩展性
多表支持（
CONFIG_IP_MROUTE_MULTIPLE_TABLES）struct mr_table *ipmr_new_table(struct net *net, u32 id) {// 创建独立路由表 }支持VRF场景，实现网络隔离。
RCU+哈希表检索
struct mfc_cache *ipmr_cache_find(struct mr_table *mrt,__be32 origin, __be32 mcastgrp) {// RCU保护的哈希查找 }实现百万级路由条目下的微秒级检索。
动态定时器管理
仅当存在未解析条目时激活定时器，减少空转开销。
六、实战洞察：定位多播问题的关键点
查看路由表
cat /proc/net/ip_mr_cache # 输出示例： # Group Origin Iif Pkts Bytes Wrong Oifs # E0000001 C0A80101 2 104 8576 0 1:3
关注"Wrong Oifs"计数，高数值表明接口配置错误。
监控虚拟接口
cat /proc/net/ip_mr_vif # 输出示例： # Interface BytesIn PktsIn BytesOut PktsOut Flags # vif0 15MB 1200 12MB 900 VIFF_TUNNEL
异常字节数指示路由环路或配置错误。
动态调试
启用内核调试选项：echo 1 > /proc/sys/net/ipv4/route/mcast_debug
结语
Linux的IPv4多播路由通过分层架构和动态管理机制，在复杂网络环境中实现了高效稳定的数据分发。其核心设计思想包括：
控制与转发分离：用户态协议处理+内核态快速转发
时间空间平衡：哈希表+链表的混合存储结构
惰性计算：按需激活处理流程
这些设计使得Linux成为从数据中心到电信网络的多播解决方案基石，为5G网络、IPTV等场景提供了关键基础设施支持。
/** IP multicast routing support for mrouted 3.6/3.8** (c) 1995 Alan Cox, <alan@lxorguk.ukuu.org.uk>* Linux Consultancy and Custom Driver Development** This program is free software; you can redistribute it and/or* modify it under the terms of the GNU General Public License* as published by the Free Software Foundation; either version* 2 of the License, or (at your option) any later version.** Fixes:* Michael Chastain : Incorrect size of copying.* Alan Cox : Added the cache manager code* Alan Cox : Fixed the clone/copy bug and device race.* Mike McLagan : Routing by source* Malcolm Beattie : Buffer handling fixes.* Alexey Kuznetsov : Double buffer free and other fixes.* SVR Anand : Fixed several multicast bugs and problems.* Alexey Kuznetsov : Status, optimisations and more.* Brad Parker : Better behaviour on mrouted upcall* overflow.* Carlos Picoto : PIMv1 Support* Pavlin Ivanov Radoslavov: PIMv2 Registers must checksum only PIM header* Relax this requirement to work with older peers.**/#include <linux/uaccess.h>
#include <linux/types.h>
#include <linux/cache.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/igmp.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/mroute.h>
#include <linux/init.h>
#include <linux/if_ether.h>
#include <linux/slab.h>
#include <net/net_namespace.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
#include <net/route.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/raw.h>
#include <linux/notifier.h>
#include <linux/if_arp.h>
#include <linux/netfilter_ipv4.h>
#include <linux/compat.h>
#include <linux/export.h>
#include <linux/rhashtable.h>
#include <net/ip_tunnels.h>
#include <net/checksum.h>
#include <net/netlink.h>
#include <net/fib_rules.h>
#include <linux/netconf.h>
#include <net/nexthop.h>
#include <net/switchdev.h>#include <linux/nospec.h>struct ipmr_rule {struct fib_rule common;
};struct ipmr_result {struct mr_table *mrt;
};/* Big lock, protecting vif table, mrt cache and mroute socket state.* Note that the changes are semaphored via rtnl_lock.*/static DEFINE_RWLOCK(mrt_lock);/* Multicast router control variables *//* Special spinlock for queue of unresolved entries */
static DEFINE_SPINLOCK(mfc_unres_lock);/* We return to original Alan's scheme. Hash table of resolved* entries is changed only in process context and protected* with weak lock mrt_lock. Queue of unresolved entries is protected* with strong spinlock mfc_unres_lock.** In this case data path is free of exclusive locks at all.*/static struct kmem_cache *mrt_cachep __ro_after_init;static struct mr_table *ipmr_new_table(struct net *net, u32 id);
static void ipmr_free_table(struct mr_table *mrt);static void ip_mr_forward(struct net *net, struct mr_table *mrt,struct net_device *dev, struct sk_buff *skb,struct mfc_cache *cache, int local);
static int ipmr_cache_report(struct mr_table *mrt,struct sk_buff *pkt, vifi_t vifi, int assert);
static void mroute_netlink_event(struct mr_table *mrt, struct mfc_cache *mfc,int cmd);
static void igmpmsg_netlink_event(struct mr_table *mrt, struct sk_buff *pkt);
static void mroute_clean_tables(struct mr_table *mrt, bool all);
static void ipmr_expire_process(struct timer_list *t);#ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLES
#define ipmr_for_each_table(mrt, net) \list_for_each_entry_rcu(mrt, &net->ipv4.mr_tables, list)static struct mr_table *ipmr_mr_table_iter(struct net *net,struct mr_table *mrt)
{struct mr_table *ret;if (!mrt)ret = list_entry_rcu(net->ipv4.mr_tables.next,struct mr_table, list);elseret = list_entry_rcu(mrt->list.next,struct mr_table, list);if (&ret->list == &net->ipv4.mr_tables)return NULL;return ret;
}static struct mr_table *ipmr_get_table(struct net *net, u32 id)
{struct mr_table *mrt;ipmr_for_each_table(mrt, net) {if (mrt->id == id)return mrt;}return NULL;
}static int ipmr_fib_lookup(struct net *net, struct flowi4 *flp4,struct mr_table **mrt)
{int err;struct ipmr_result res;struct fib_lookup_arg arg = {.result = &res,.flags = FIB_LOOKUP_NOREF,};/* update flow if oif or iif point to device enslaved to l3mdev */l3mdev_update_flow(net, flowi4_to_flowi(flp4));err = fib_rules_lookup(net->ipv4.mr_rules_ops,flowi4_to_flowi(flp4), 0, &arg);if (err < 0)return err;*mrt = res.mrt;return 0;
}static int ipmr_rule_action(struct fib_rule *rule, struct flowi *flp,int flags, struct fib_lookup_arg *arg)
{struct ipmr_result *res = arg->result;struct mr_table *mrt;switch (rule->action) {case FR_ACT_TO_TBL:break;case FR_ACT_UNREACHABLE:return -ENETUNREACH;case FR_ACT_PROHIBIT:return -EACCES;case FR_ACT_BLACKHOLE:default:return -EINVAL;}arg->table = fib_rule_get_table(rule, arg);mrt = ipmr_get_table(rule->fr_net, arg->table);if (!mrt)return -EAGAIN;res->mrt = mrt;return 0;
}static int ipmr_rule_match(struct fib_rule *rule, struct flowi *fl, int flags)
{return 1;
}static const struct nla_policy ipmr_rule_policy[FRA_MAX + 1] = {FRA_GENERIC_POLICY,
};static int ipmr_rule_configure(struct fib_rule *rule, struct sk_buff *skb,struct fib_rule_hdr *frh, struct nlattr **tb,struct netlink_ext_ack *extack)
{return 0;
}static int ipmr_rule_compare(struct fib_rule *rule, struct fib_rule_hdr *frh,struct nlattr **tb)
{return 1;
}static int ipmr_rule_fill(struct fib_rule *rule, struct sk_buff *skb,struct fib_rule_hdr *frh)
{frh->dst_len = 0;frh->src_len = 0;frh->tos = 0;return 0;
}static const struct fib_rules_ops __net_initconst ipmr_rules_ops_template = {.family = RTNL_FAMILY_IPMR,.rule_size = sizeof(struct ipmr_rule),.addr_size = sizeof(u32),.action = ipmr_rule_action,.match = ipmr_rule_match,.configure = ipmr_rule_configure,.compare = ipmr_rule_compare,.fill = ipmr_rule_fill,.nlgroup = RTNLGRP_IPV4_RULE,.policy = ipmr_rule_policy,.owner = THIS_MODULE,
};static int __net_init ipmr_rules_init(struct net *net)
{struct fib_rules_ops *ops;struct mr_table *mrt;int err;ops = fib_rules_register(&ipmr_rules_ops_template, net);if (IS_ERR(ops))return PTR_ERR(ops);INIT_LIST_HEAD(&net->ipv4.mr_tables);mrt = ipmr_new_table(net, RT_TABLE_DEFAULT);if (IS_ERR(mrt)) {err = PTR_ERR(mrt);goto err1;}err = fib_default_rule_add(ops, 0x7fff, RT_TABLE_DEFAULT, 0);if (err < 0)goto err2;net->ipv4.mr_rules_ops = ops;return 0;err2:ipmr_free_table(mrt);
err1:fib_rules_unregister(ops);return err;
}static void __net_exit ipmr_rules_exit(struct net *net)
{struct mr_table *mrt, *next;rtnl_lock();list_for_each_entry_safe(mrt, next, &net->ipv4.mr_tables, list) {list_del(&mrt->list);ipmr_free_table(mrt);}fib_rules_unregister(net->ipv4.mr_rules_ops);rtnl_unlock();
}static int ipmr_rules_dump(struct net *net, struct notifier_block *nb)
{return fib_rules_dump(net, nb, RTNL_FAMILY_IPMR);
}static unsigned int ipmr_rules_seq_read(struct net *net)
{return fib_rules_seq_read(net, RTNL_FAMILY_IPMR);
}bool ipmr_rule_default(const struct fib_rule *rule)
{return fib_rule_matchall(rule) && rule->table == RT_TABLE_DEFAULT;
}
EXPORT_SYMBOL(ipmr_rule_default);
#else
#define ipmr_for_each_table(mrt, net) \for (mrt = net->ipv4.mrt; mrt; mrt = NULL)static struct mr_table *ipmr_mr_table_iter(struct net *net,struct mr_table *mrt)
{if (!mrt)return net->ipv4.mrt;return NULL;
}static struct mr_table *ipmr_get_table(struct net *net, u32 id)
{return net->ipv4.mrt;
}static int ipmr_fib_lookup(struct net *net, struct flowi4 *flp4,struct mr_table **mrt)
{*mrt = net->ipv4.mrt;return 0;
}static int __net_init ipmr_rules_init(struct net *net)
{struct mr_table *mrt;mrt = ipmr_new_table(net, RT_TABLE_DEFAULT);if (IS_ERR(mrt))return PTR_ERR(mrt);net->ipv4.mrt = mrt;return 0;
}static void __net_exit ipmr_rules_exit(struct net *net)
{rtnl_lock();ipmr_free_table(net->ipv4.mrt);net->ipv4.mrt = NULL;rtnl_unlock();
}static int ipmr_rules_dump(struct net *net, struct notifier_block *nb)
{return 0;
}static unsigned int ipmr_rules_seq_read(struct net *net)
{return 0;
}bool ipmr_rule_default(const struct fib_rule *rule)
{return true;
}
EXPORT_SYMBOL(ipmr_rule_default);
#endifstatic inline int ipmr_hash_cmp(struct rhashtable_compare_arg *arg,const void *ptr)
{const struct mfc_cache_cmp_arg *cmparg = arg->key;struct mfc_cache *c = (struct mfc_cache *)ptr;return cmparg->mfc_mcastgrp != c->mfc_mcastgrp ||cmparg->mfc_origin != c->mfc_origin;
}static const struct rhashtable_params ipmr_rht_params = {.head_offset = offsetof(struct mr_mfc, mnode),.key_offset = offsetof(struct mfc_cache, cmparg),.key_len = sizeof(struct mfc_cache_cmp_arg),.nelem_hint = 3,.locks_mul = 1,.obj_cmpfn = ipmr_hash_cmp,.automatic_shrinking = true,
};static void ipmr_new_table_set(struct mr_table *mrt,struct net *net)
{
#ifdef CONFIG_IP_MROUTE_MULTIPLE_TABLESlist_add_tail_rcu(&mrt->list, &net->ipv4.mr_tables);
#endif
}static struct mfc_cache_cmp_arg ipmr_mr_table_ops_cmparg_any = {.mfc_mcastgrp = htonl(INADDR_ANY),.mfc_origin = htonl(INADDR_ANY),
};static struct mr_table_ops ipmr_mr_table_ops = {.rht_params = &ipmr_rht_params,.cmparg_any = &ipmr_mr_table_ops_cmparg_any,
};static struct mr_table *ipmr_new_table(struct net *net, u32 id)
{struct mr_table *mrt;/* "pimreg%u" should not exceed 16 bytes (IFNAMSIZ) */if (id != RT_TABLE_DEFAULT && id >= 1000000000)return ERR_PTR(-EINVAL);mrt = ipmr_get_table(net, id);if (mrt)return mrt;return mr_table_alloc(net, id, &ipmr_mr_table_ops,ipmr_expire_process, ipmr_new_table_set);
}static void ipmr_free_table(struct mr_table *mrt)
{del_timer_sync(&mrt->ipmr_expire_timer);mroute_clean_tables(mrt, true);rhltable_destroy(&mrt->mfc_hash);kfree(mrt);
}/* Service routines creating virtual interfaces: DVMRP tunnels and PIMREG */static void ipmr_del_tunnel(struct net_device *dev, struct vifctl *v)
{struct net *net = dev_net(dev);dev_close(dev);dev = __dev_get_by_name(net, "tunl0");if (dev) {const struct net_device_ops *ops = dev->netdev_ops;struct ifreq ifr;struct ip_tunnel_parm p;memset(&p, 0, sizeof(p));p.iph.daddr = v->vifc_rmt_addr.s_addr;p.iph.saddr = v->vifc_lcl_addr.s_addr;p.iph.version = 4;p.iph.ihl = 5;p.iph.protocol = IPPROTO_IPIP;sprintf(p.name, "dvmrp%d", v->vifc_vifi);ifr.ifr_ifru.ifru_data = (__force void __user *)&p;if (ops->ndo_do_ioctl) {mm_segment_t oldfs = get_fs();set_fs(KERNEL_DS);ops->ndo_do_ioctl(dev, &ifr, SIOCDELTUNNEL);set_fs(oldfs);}}
}/* Initialize ipmr pimreg/tunnel in_device */
static bool ipmr_init_vif_indev(const struct net_device *dev)
{struct in_device *in_dev;ASSERT_RTNL();in_dev = __in_dev_get_rtnl(dev);if (!in_dev)return false;ipv4_devconf_setall(in_dev);neigh_parms_data_state_setall(in_dev->arp_parms);IPV4_DEVCONF(in_dev->cnf, RP_FILTER) = 0;return true;
}static struct net_device *ipmr_new_tunnel(struct net *net, struct vifctl *v)
{struct net_device *dev;dev = __dev_get_by_name(net, "tunl0");if (dev) {const struct net_device_ops *ops = dev->netdev_ops;int err;struct ifreq ifr;struct ip_tunnel_parm p;memset(&p, 0, sizeof(p));p.iph.daddr = v->vifc_rmt_addr.s_addr;p.iph.saddr = v->vifc_lcl_addr.s_addr;p.iph.version = 4;p.iph.ihl = 5;p.iph.protocol = IPPROTO_IPIP;sprintf(p.name, "dvmrp%d", v->vifc_vifi);ifr.ifr_ifru.ifru_data = (__force void __user *)&p;if (ops->ndo_do_ioctl) {mm_segment_t oldfs = get_fs();set_fs(KERNEL_DS);err = ops->ndo_do_ioctl(dev, &ifr, SIOCADDTUNNEL);set_fs(oldfs);} else {err = -EOPNOTSUPP;}dev = NULL;if (err == 0 &&(dev = __dev_get_by_name(net, p.name)) != NULL) {dev->flags |= IFF_MULTICAST;if (!ipmr_init_vif_indev(dev))goto failure;if (dev_open(dev))goto failure;dev_hold(dev);}}return dev;failure:unregister_netdevice(dev);return NULL;
}#if defined(CONFIG_IP_PIMSM_V1) || defined(CONFIG_IP_PIMSM_V2)
static netdev_tx_t reg_vif_xmit(struct sk_buff *skb, struct net_device *dev)
{struct net *net = dev_net(dev);struct mr_table *mrt;struct flowi4 fl4 = {.flowi4_oif = dev->ifindex,.flowi4_iif = skb->skb_iif ? : LOOPBACK_IFINDEX,.flowi4_mark = skb->mark,};int err;err = ipmr_fib_lookup(net, &fl4, &mrt);if (err < 0) {kfree_skb(skb);return err;}read_lock(&mrt_lock);dev->stats.tx_bytes += skb->len;dev->stats.tx_packets++;ipmr_cache_report(mrt, skb, mrt->mroute_reg_vif_num, IGMPMSG_WHOLEPKT);read_unlock(&mrt_lock);kfree_skb(skb);return NETDEV_TX_OK;
}static int reg_vif_get_iflink(const struct net_device *dev)
{return 0;
}static const struct net_device_ops reg_vif_netdev_ops = {.ndo_start_xmit = reg_vif_xmit,.ndo_get_iflink = reg_vif_get_iflink,
};static void reg_vif_setup(struct net_device *dev)
{dev->type = ARPHRD_PIMREG;dev->mtu = ETH_DATA_LEN - sizeof(struct iphdr) - 8;dev->flags = IFF_NOARP;dev->netdev_ops = ®_vif_netdev_ops;dev->needs_free_netdev = true;dev->features |= NETIF_F_NETNS_LOCAL;
}static struct net_device *ipmr_reg_vif(struct net *net, struct mr_table *mrt)
{struct net_device *dev;char name[IFNAMSIZ];if (mrt->id == RT_TABLE_DEFAULT)sprintf(name, "pimreg");elsesprintf(name, "pimreg%u", mrt->id);dev = alloc_netdev(0, name, NET_NAME_UNKNOWN, reg_vif_setup);if (!dev)return NULL;dev_net_set(dev, net);if (register_netdevice(dev)) {free_netdev(dev);return NULL;}if (!ipmr_init_vif_indev(dev))goto failure;if (dev_open(dev))goto failure;dev_hold(dev);return dev;failure:unregister_netdevice(dev);return NULL;
}/* called with rcu_read_lock() */
static int __pim_rcv(struct mr_table *mrt, struct sk_buff *skb,unsigned int pimlen)
{struct net_device *reg_dev = NULL;struct iphdr *encap;encap = (struct iphdr *)(skb_transport_header(skb) + pimlen);/* Check that:* a. packet is really sent to a multicast group* b. packet is not a NULL-REGISTER* c. packet is not truncated*/if (!ipv4_is_multicast(encap->daddr) ||encap->tot_len == 0 ||ntohs(encap->tot_len) + pimlen > skb->len)return 1;read_lock(&mrt_lock);if (mrt->mroute_reg_vif_num >= 0)reg_dev = mrt->vif_table[mrt->mroute_reg_vif_num].dev;read_unlock(&mrt_lock);if (!reg_dev)return 1;skb->mac_header = skb->network_header;skb_pull(skb, (u8 *)encap - skb->data);skb_reset_network_header(skb);skb->protocol = htons(ETH_P_IP);skb->ip_summed = CHECKSUM_NONE;skb_tunnel_rx(skb, reg_dev, dev_net(reg_dev));netif_rx(skb);return NET_RX_SUCCESS;
}
#else
static struct net_device *ipmr_reg_vif(struct net *net, struct mr_table *mrt)
{return NULL;
}
#endifstatic int call_ipmr_vif_entry_notifiers(struct net *net,enum fib_event_type event_type,struct vif_device *vif,vifi_t vif_index, u32 tb_id)
{return mr_call_vif_notifiers(net, RTNL_FAMILY_IPMR, event_type,vif, vif_index, tb_id,&net->ipv4.ipmr_seq);
}static int call_ipmr_mfc_entry_notifiers(struct net *net,enum fib_event_type event_type,struct mfc_cache *mfc, u32 tb_id)
{return mr_call_mfc_notifiers(net, RTNL_FAMILY_IPMR, event_type,&mfc->_c, tb_id, &net->ipv4.ipmr_seq);
}/*** vif_delete - Delete a VIF entry* @notify: Set to 1, if the caller is a notifier_call*/
static int vif_delete(struct mr_table *mrt, int vifi, int notify,struct list_head *head)
{struct net *net = read_pnet(&mrt->net);struct vif_device *v;struct net_device *dev;struct in_device *in_dev;if (vifi < 0 || vifi >= mrt->maxvif)return -EADDRNOTAVAIL;v = &mrt->vif_table[vifi];if (VIF_EXISTS(mrt, vifi))call_ipmr_vif_entry_notifiers(net, FIB_EVENT_VIF_DEL, v, vifi,mrt->id);write_lock_bh(&mrt_lock);dev = v->dev;v->dev = NULL;if (!dev) {write_unlock_bh(&mrt_lock);return -EADDRNOTAVAIL;}if (vifi == mrt->mroute_reg_vif_num)mrt->mroute_reg_vif_num = -1;if (vifi + 1 == mrt->maxvif) {int tmp;for (tmp = vifi - 1; tmp >= 0; tmp--) {if (VIF_EXISTS(mrt, tmp))break;}mrt->maxvif = tmp+1;}write_unlock_bh(&mrt_lock);dev_set_allmulti(dev, -1);in_dev = __in_dev_get_rtnl(dev);if (in_dev) {IPV4_DEVCONF(in_dev->cnf, MC_FORWARDING)--;inet_netconf_notify_devconf(dev_net(dev), RTM_NEWNETCONF,NETCONFA_MC_FORWARDING,dev->ifindex, &in_dev->cnf);ip_rt_multicast_event(in_dev);}if (v->flags & (VIFF_TUNNEL | VIFF_REGISTER) && !notify)unregister_netdevice_queue(dev, head);dev_put(dev);return 0;
}static void ipmr_cache_free_rcu(struct rcu_head *head)
{struct mr_mfc *c = container_of(head, struct mr_mfc, rcu);kmem_cache_free(mrt_cachep, (struct mfc_cache *)c);
}static void ipmr_cache_free(struct mfc_cache *c)
{call_rcu(&c->_c.rcu, ipmr_cache_free_rcu);
}/* Destroy an unresolved cache entry, killing queued skbs* and reporting error to netlink readers.*/
static void ipmr_destroy_unres(struct mr_table *mrt, struct mfc_cache *c)
{struct net *net = read_pnet(&mrt->net);struct sk_buff *skb;struct nlmsgerr *e;atomic_dec(&mrt->cache_resolve_queue_len);while ((skb = skb_dequeue(&c->_c.mfc_un.unres.unresolved))) {if (ip_hdr(skb)->version == 0) {struct nlmsghdr *nlh = skb_pull(skb,sizeof(struct iphdr));nlh->nlmsg_type = NLMSG_ERROR;nlh->nlmsg_len = nlmsg_msg_size(sizeof(struct nlmsgerr));skb_trim(skb, nlh->nlmsg_len);e = nlmsg_data(nlh);e->error = -ETIMEDOUT;memset(&e->msg, 0, sizeof(e->msg));rtnl_unicast(skb, net, NETLINK_CB(skb).portid);} else {kfree_skb(skb);}}ipmr_cache_free(c);
}/* Timer process for the unresolved queue. */
static void ipmr_expire_process(struct timer_list *t)
{struct mr_table *mrt = from_timer(mrt, t, ipmr_expire_timer);struct mr_mfc *c, *next;unsigned long expires;unsigned long now;if (!spin_trylock(&mfc_unres_lock)) {mod_timer(&mrt->ipmr_expire_timer, jiffies+HZ/10);return;}if (list_empty(&mrt->mfc_unres_queue))goto out;now = jiffies;expires = 10*HZ;list_for_each_entry_safe(c, next, &mrt->mfc_unres_queue, list) {if (time_after(c->mfc_un.unres.expires, now)) {unsigned long interval = c->mfc_un.unres.expires - now;if (interval < expires)expires = interval;continue;}list_del(&c->list);mroute_netlink_event(mrt, (struct mfc_cache *)c, RTM_DELROUTE);ipmr_destroy_unres(mrt, (struct mfc_cache *)c);}if (!list_empty(&mrt->mfc_unres_queue))mod_timer(&mrt->ipmr_expire_timer, jiffies + expires);out:spin_unlock(&mfc_unres_lock);
}/* Fill oifs list. It is called under write locked mrt_lock. */
static void ipmr_update_thresholds(struct mr_table *mrt, struct mr_mfc *cache,unsigned char *ttls)
{int vifi;cache->mfc_un.res.minvif = MAXVIFS;cache->mfc_un.res.maxvif = 0;memset(cache->mfc_un.res.ttls, 255, MAXVIFS);for (vifi = 0; vifi < mrt->maxvif; vifi++) {if (VIF_EXISTS(mrt, vifi) &&ttls[vifi] && ttls[vifi] < 255) {cache->mfc_un.res.ttls[vifi] = ttls[vifi];if (cache->mfc_un.res.minvif > vifi)cache->mfc_un.res.minvif = vifi;if (cache->mfc_un.res.maxvif <= vifi)cache->mfc_un.res.maxvif = vifi + 1;}}cache->mfc_un.res.lastuse = jiffies;
}static int vif_add(struct net *net, struct mr_table *mrt,struct vifctl *vifc, int mrtsock)
{int vifi = vifc->vifc_vifi;struct switchdev_attr attr = {.id = SWITCHDEV_ATTR_ID_PORT_PARENT_ID,};struct vif_device *v = &mrt->vif_table[vifi];struct net_device *dev;struct in_device *in_dev;int err;/* Is vif busy ? */if (VIF_EXISTS(mrt, vifi))return -EADDRINUSE;switch (vifc->vifc_flags) {case VIFF_REGISTER:if (!ipmr_pimsm_enabled())return -EINVAL;/* Special Purpose VIF in PIM* All the packets will be sent to the daemon*/if (mrt->mroute_reg_vif_num >= 0)return -EADDRINUSE;dev = ipmr_reg_vif(net, mrt);if (!dev)return -ENOBUFS;err = dev_set_allmulti(dev, 1);if (err) {unregister_netdevice(dev);dev_put(dev);return err;}break;case VIFF_TUNNEL:dev = ipmr_new_tunnel(net, vifc);if (!dev)return -ENOBUFS;err = dev_set_allmulti(dev, 1);if (err) {ipmr_del_tunnel(dev, vifc);dev_put(dev);return err;}break;case VIFF_USE_IFINDEX:case 0:if (vifc->vifc_flags == VIFF_USE_IFINDEX) {dev = dev_get_by_index(net, vifc->vifc_lcl_ifindex);if (dev && !__in_dev_get_rtnl(dev)) {dev_put(dev);return -EADDRNOTAVAIL;}} else {dev = ip_dev_find(net, vifc->vifc_lcl_addr.s_addr);}if (!dev)return -EADDRNOTAVAIL;err = dev_set_allmulti(dev, 1);if (err) {dev_put(dev);return err;}break;default:return -EINVAL;}in_dev = __in_dev_get_rtnl(dev);if (!in_dev) {dev_put(dev);return -EADDRNOTAVAIL;}IPV4_DEVCONF(in_dev->cnf, MC_FORWARDING)++;inet_netconf_notify_devconf(net, RTM_NEWNETCONF, NETCONFA_MC_FORWARDING,dev->ifindex, &in_dev->cnf);ip_rt_multicast_event(in_dev);/* Fill in the VIF structures */vif_device_init(v, dev, vifc->vifc_rate_limit,vifc->vifc_threshold,vifc->vifc_flags | (!mrtsock ? VIFF_STATIC : 0),(VIFF_TUNNEL | VIFF_REGISTER));attr.orig_dev = dev;if (!switchdev_port_attr_get(dev, &attr)) {memcpy(v->dev_parent_id.id, attr.u.ppid.id, attr.u.ppid.id_len);v->dev_parent_id.id_len = attr.u.ppid.id_len;} else {v->dev_parent_id.id_len = 0;}v->local = vifc->vifc_lcl_addr.s_addr;v->remote = vifc->vifc_rmt_addr.s_addr;/* And finish update writing critical data */write_lock_bh(&mrt_lock);v->dev = dev;if (v->flags & VIFF_REGISTER)mrt->mroute_reg_vif_num = vifi;if (vifi+1 > mrt->maxvif)mrt->maxvif = vifi+1;write_unlock_bh(&mrt_lock);call_ipmr_vif_entry_notifiers(net, FIB_EVENT_VIF_ADD, v, vifi, mrt->id);return 0;
}/* called with rcu_read_lock() */
static struct mfc_cache *ipmr_cache_find(struct mr_table *mrt,__be32 origin,__be32 mcastgrp)
{struct mfc_cache_cmp_arg arg = {.mfc_mcastgrp = mcastgrp,.mfc_origin = origin};return mr_mfc_find(mrt, &arg);
}/* Look for a (*,G) entry */
static struct mfc_cache *ipmr_cache_find_any(struct mr_table *mrt,__be32 mcastgrp, int vifi)
{struct mfc_cache_cmp_arg arg = {.mfc_mcastgrp = mcastgrp,.mfc_origin = htonl(INADDR_ANY)};if (mcastgrp == htonl(INADDR_ANY))return mr_mfc_find_any_parent(mrt, vifi);return mr_mfc_find_any(mrt, vifi, &arg);
}/* Look for a (S,G,iif) entry if parent != -1 */
static struct mfc_cache *ipmr_cache_find_parent(struct mr_table *mrt,__be32 origin, __be32 mcastgrp,int parent)
{struct mfc_cache_cmp_arg arg = {.mfc_mcastgrp = mcastgrp,.mfc_origin = origin,};return mr_mfc_find_parent(mrt, &arg, parent);
}/* Allocate a multicast cache entry */
static struct mfc_cache *ipmr_cache_alloc(void)
{struct mfc_cache *c = kmem_cache_zalloc(mrt_cachep, GFP_KERNEL);if (c) {c->_c.mfc_un.res.last_assert = jiffies - MFC_ASSERT_THRESH - 1;c->_c.mfc_un.res.minvif = MAXVIFS;c->_c.free = ipmr_cache_free_rcu;refcount_set(&c->_c.mfc_un.res.refcount, 1);}return c;
}static struct mfc_cache *ipmr_cache_alloc_unres(void)
{struct mfc_cache *c = kmem_cache_zalloc(mrt_cachep, GFP_ATOMIC);if (c) {skb_queue_head_init(&c->_c.mfc_un.unres.unresolved);c->_c.mfc_un.unres.expires = jiffies + 10 * HZ;}return c;
}/* A cache entry has gone into a resolved state from queued */
static void ipmr_cache_resolve(struct net *net, struct mr_table *mrt,struct mfc_cache *uc, struct mfc_cache *c)
{struct sk_buff *skb;struct nlmsgerr *e;/* Play the pending entries through our router */while ((skb = __skb_dequeue(&uc->_c.mfc_un.unres.unresolved))) {if (ip_hdr(skb)->version == 0) {struct nlmsghdr *nlh = skb_pull(skb,sizeof(struct iphdr));if (mr_fill_mroute(mrt, skb, &c->_c,nlmsg_data(nlh)) > 0) {nlh->nlmsg_len = skb_tail_pointer(skb) -(u8 *)nlh;} else {nlh->nlmsg_type = NLMSG_ERROR;nlh->nlmsg_len = nlmsg_msg_size(sizeof(struct nlmsgerr));skb_trim(skb, nlh->nlmsg_len);e = nlmsg_data(nlh);e->error = -EMSGSIZE;memset(&e->msg, 0, sizeof(e->msg));}rtnl_unicast(skb, net, NETLINK_CB(skb).portid);} else {ip_mr_forward(net, mrt, skb->dev, skb, c, 0);}}
}/* Bounce a cache query up to mrouted and netlink.** Called under mrt_lock.*/
static int ipmr_cache_report(struct mr_table *mrt,struct sk_buff *pkt, vifi_t vifi, int assert)
{const int ihl = ip_hdrlen(pkt);struct sock *mroute_sk;struct igmphdr *igmp;struct igmpmsg *msg;struct sk_buff *skb;int ret;if (assert == IGMPMSG_WHOLEPKT || assert == IGMPMSG_WRVIFWHOLE)skb = skb_realloc_headroom(pkt, sizeof(struct iphdr));elseskb = alloc_skb(128, GFP_ATOMIC);if (!skb)return -ENOBUFS;if (assert == IGMPMSG_WHOLEPKT || assert == IGMPMSG_WRVIFWHOLE) {/* Ugly, but we have no choice with this interface.* Duplicate old header, fix ihl, length etc.* And all this only to mangle msg->im_msgtype and* to set msg->im_mbz to "mbz" :-)*/skb_push(skb, sizeof(struct iphdr));skb_reset_network_header(skb);skb_reset_transport_header(skb);msg = (struct igmpmsg *)skb_network_header(skb);memcpy(msg, skb_network_header(pkt), sizeof(struct iphdr));msg->im_msgtype = assert;msg->im_mbz = 0;if (assert == IGMPMSG_WRVIFWHOLE)msg->im_vif = vifi;elsemsg->im_vif = mrt->mroute_reg_vif_num;ip_hdr(skb)->ihl = sizeof(struct iphdr) >> 2;ip_hdr(skb)->tot_len = htons(ntohs(ip_hdr(pkt)->tot_len) +sizeof(struct iphdr));} else {/* Copy the IP header */skb_set_network_header(skb, skb->len);skb_put(skb, ihl);skb_copy_to_linear_data(skb, pkt->data, ihl);/* Flag to the kernel this is a route add */ip_hdr(skb)->protocol = 0;msg = (struct igmpmsg *)skb_network_header(skb);msg->im_vif = vifi;skb_dst_set(skb, dst_clone(skb_dst(pkt)));/* Add our header */igmp = skb_put(skb, sizeof(struct igmphdr));igmp->type = assert;msg->im_msgtype = assert;igmp->code = 0;ip_hdr(skb)->tot_len = htons(skb->len); /* Fix the length */skb->transport_header = skb->network_header;}rcu_read_lock();mroute_sk = rcu_dereference(mrt->mroute_sk);if (!mroute_sk) {rcu_read_unlock();kfree_skb(skb);return -EINVAL;}igmpmsg_netlink_event(mrt, skb);/* Deliver to mrouted */ret = sock_queue_rcv_skb(mroute_sk, skb);rcu_read_unlock();if (ret < 0) {net_warn_ratelimited("mroute: pending queue full, dropping entries\n");kfree_skb(skb);}return ret;
}/* Queue a packet for resolution. It gets locked cache entry! */
static int ipmr_cache_unresolved(struct mr_table *mrt, vifi_t vifi,struct sk_buff *skb, struct net_device *dev)
{const struct iphdr *iph = ip_hdr(skb);struct mfc_cache *c;bool found = false;int err;spin_lock_bh(&mfc_unres_lock);list_for_each_entry(c, &mrt->mfc_unres_queue, _c.list) {if (c->mfc_mcastgrp == iph->daddr &&c->mfc_origin == iph->saddr) {found = true;break;}}if (!found) {/* Create a new entry if allowable */if (atomic_read(&mrt->cache_resolve_queue_len) >= 10 ||(c = ipmr_cache_alloc_unres()) == NULL) {spin_unlock_bh(&mfc_unres_lock);kfree_skb(skb);return -ENOBUFS;}/* Fill in the new cache entry */c->_c.mfc_parent = -1;c->mfc_origin = iph->saddr;c->mfc_mcastgrp = iph->daddr;/* Reflect first query at mrouted. */err = ipmr_cache_report(mrt, skb, vifi, IGMPMSG_NOCACHE);if (err < 0) {/* If the report failed throw the cache entryout - Brad Parker*/spin_unlock_bh(&mfc_unres_lock);ipmr_cache_free(c);kfree_skb(skb);return err;}atomic_inc(&mrt->cache_resolve_queue_len);list_add(&c->_c.list, &mrt->mfc_unres_queue);mroute_netlink_event(mrt, c, RTM_NEWROUTE);if (atomic_read(&mrt->cache_resolve_queue_len) == 1)mod_timer(&mrt->ipmr_expire_timer,c->_c.mfc_un.unres.expires);}/* See if we can append the packet */if (c->_c.mfc_un.unres.unresolved.qlen > 3) {kfree_skb(skb);err = -ENOBUFS;} else {if (dev) {skb->dev = dev;skb->skb_iif = dev->ifindex;}skb_queue_tail(&c->_c.mfc_un.unres.unresolved, skb);err = 0;}spin_unlock_bh(&mfc_unres_lock);return err;
}/* MFC cache manipulation by user space mroute daemon */static int ipmr_mfc_delete(struct mr_table *mrt, struct mfcctl *mfc, int parent)
{struct net *net = read_pnet(&mrt->net);struct mfc_cache *c;/* The entries are added/deleted only under RTNL */rcu_read_lock();c = ipmr_cache_find_parent(mrt, mfc->mfcc_origin.s_addr,mfc->mfcc_mcastgrp.s_addr, parent);rcu_read_unlock();if (!c)return -ENOENT;rhltable_remove(&mrt->mfc_hash, &c->_c.mnode, ipmr_rht_params);list_del_rcu(&c->_c.list);call_ipmr_mfc_entry_notifiers(net, FIB_EVENT_ENTRY_DEL, c, mrt->id);mroute_netlink_event(mrt, c, RTM_DELROUTE);mr_cache_put(&c->_c);return 0;
}static int ipmr_mfc_add(struct net *net, struct mr_table *mrt,struct mfcctl *mfc, int mrtsock, int parent)
{struct mfc_cache *uc, *c;struct mr_mfc *_uc;bool found;int ret;if (mfc->mfcc_parent >= MAXVIFS)return -ENFILE;/* The entries are added/deleted only under RTNL */rcu_read_lock();c = ipmr_cache_find_parent(mrt, mfc->mfcc_origin.s_addr,mfc->mfcc_mcastgrp.s_addr, parent);rcu_read_unlock();if (c) {write_lock_bh(&mrt_lock);c->_c.mfc_parent = mfc->mfcc_parent;ipmr_update_thresholds(mrt, &c->_c, mfc->mfcc_ttls);if (!mrtsock)c->_c.mfc_flags |= MFC_STATIC;write_unlock_bh(&mrt_lock);call_ipmr_mfc_entry_notifiers(net, FIB_EVENT_ENTRY_REPLACE, c,mrt->id);mroute_netlink_event(mrt, c, RTM_NEWROUTE);return 0;}if (mfc->mfcc_mcastgrp.s_addr != htonl(INADDR_ANY) &&!ipv4_is_multicast(mfc->mfcc_mcastgrp.s_addr))return -EINVAL;c = ipmr_cache_alloc();if (!c)return -ENOMEM;c->mfc_origin = mfc->mfcc_origin.s_addr;c->mfc_mcastgrp = mfc->mfcc_mcastgrp.s_addr;c->_c.mfc_parent = mfc->mfcc_parent;ipmr_update_thresholds(mrt, &c->_c, mfc->mfcc_ttls);if (!mrtsock)c->_c.mfc_flags |= MFC_STATIC;ret = rhltable_insert_key(&mrt->mfc_hash, &c->cmparg, &c->_c.mnode,ipmr_rht_params);if (ret) {pr_err("ipmr: rhtable insert error %d\n", ret);ipmr_cache_free(c);return ret;}list_add_tail_rcu(&c->_c.list, &mrt->mfc_cache_list);/* Check to see if we resolved a queued list. If so we* need to send on the frames and tidy up.*/found = false;spin_lock_bh(&mfc_unres_lock);list_for_each_entry(_uc, &mrt->mfc_unres_queue, list) {uc = (struct mfc_cache *)_uc;if (uc->mfc_origin == c->mfc_origin &&uc->mfc_mcastgrp == c->mfc_mcastgrp) {list_del(&_uc->list);atomic_dec(&mrt->cache_resolve_queue_len);found = true;break;}}if (list_empty(&mrt->mfc_unres_queue))del_timer(&mrt->ipmr_expire_timer);spin_unlock_bh(&mfc_unres_lock);if (found) {ipmr_cache_resolve(net, mrt, uc, c);ipmr_cache_free(uc);}call_ipmr_mfc_entry_notifiers(net, FIB_EVENT_ENTRY_ADD, c, mrt->id);mroute_netlink_event(mrt, c, RTM_NEWROUTE);return 0;
}/* Close the multicast socket, and clear the vif tables etc */
static void mroute_clean_tables(struct mr_table *mrt, bool all)
{struct net *net = read_pnet(&mrt->net);struct mr_mfc *c, *tmp;struct mfc_cache *cache;LIST_HEAD(list);int i;/* Shut down all active vif entries */for (i = 0; i < mrt->maxvif; i++) {if (!all && (mrt->vif_table[i].flags & VIFF_STATIC))continue;vif_delete(mrt, i, 0, &list);}unregister_netdevice_many(&list);/* Wipe the cache */list_for_each_entry_safe(c, tmp, &mrt->mfc_cache_list, list) {if (!all && (c->mfc_flags & MFC_STATIC))continue;rhltable_remove(&mrt->mfc_hash, &c->mnode, ipmr_rht_params);list_del_rcu(&c->list);cache = (struct mfc_cache *)c;call_ipmr_mfc_entry_notifiers(net, FIB_EVENT_ENTRY_DEL, cache,mrt->id);mroute_netlink_event(mrt, cache, RTM_DELROUTE);mr_cache_put(c);}if (atomic_read(&mrt->cache_resolve_queue_len) != 0) {spin_lock_bh(&mfc_unres_lock);list_for_each_entry_safe(c, tmp, &mrt->mfc_unres_queue, list) {list_del(&c->list);cache = (struct mfc_cache *)c;mroute_netlink_event(mrt, cache, RTM_DELROUTE);ipmr_destroy_unres(mrt, cache);}spin_unlock_bh(&mfc_unres_lock);}
}/* called from ip_ra_control(), before an RCU grace period,* we dont need to call synchronize_rcu() here*/
static void mrtsock_destruct(struct sock *sk)
{struct net *net = sock_net(sk);struct mr_table *mrt;rtnl_lock();ipmr_for_each_table(mrt, net) {if (sk == rtnl_dereference(mrt->mroute_sk)) {IPV4_DEVCONF_ALL(net, MC_FORWARDING)--;inet_netconf_notify_devconf(net, RTM_NEWNETCONF,NETCONFA_MC_FORWARDING,NETCONFA_IFINDEX_ALL,net->ipv4.devconf_all);RCU_INIT_POINTER(mrt->mroute_sk, NULL);mroute_clean_tables(mrt, false);}}rtnl_unlock();
}/* Socket options and virtual interface manipulation. The whole* virtual interface system is a complete heap, but unfortunately* that's how BSD mrouted happens to think. Maybe one day with a proper* MOSPF/PIM router set up we can clean this up.*/int ip_mroute_setsockopt(struct sock *sk, int optname, char __user *optval,unsigned int optlen)
{struct net *net = sock_net(sk);int val, ret = 0, parent = 0;struct mr_table *mrt;struct vifctl vif;struct mfcctl mfc;bool do_wrvifwhole;u32 uval;/* There's one exception to the lock - MRT_DONE which needs to unlock */rtnl_lock();if (sk->sk_type != SOCK_RAW ||inet_sk(sk)->inet_num != IPPROTO_IGMP) {ret = -EOPNOTSUPP;goto out_unlock;}mrt = ipmr_get_table(net, raw_sk(sk)->ipmr_table ? : RT_TABLE_DEFAULT);if (!mrt) {ret = -ENOENT;goto out_unlock;}if (optname != MRT_INIT) {if (sk != rcu_access_pointer(mrt->mroute_sk) &&!ns_capable(net->user_ns, CAP_NET_ADMIN)) {ret = -EACCES;goto out_unlock;}}switch (optname) {case MRT_INIT:if (optlen != sizeof(int)) {ret = -EINVAL;break;}if (rtnl_dereference(mrt->mroute_sk)) {ret = -EADDRINUSE;break;}ret = ip_ra_control(sk, 1, mrtsock_destruct);if (ret == 0) {rcu_assign_pointer(mrt->mroute_sk, sk);IPV4_DEVCONF_ALL(net, MC_FORWARDING)++;inet_netconf_notify_devconf(net, RTM_NEWNETCONF,NETCONFA_MC_FORWARDING,NETCONFA_IFINDEX_ALL,net->ipv4.devconf_all);}break;case MRT_DONE:if (sk != rcu_access_pointer(mrt->mroute_sk)) {ret = -EACCES;} else {/* We need to unlock here because mrtsock_destruct takes* care of rtnl itself and we can't change that due to* the IP_ROUTER_ALERT setsockopt which runs without it.*/rtnl_unlock();ret = ip_ra_control(sk, 0, NULL);goto out;}break;case MRT_ADD_VIF:case MRT_DEL_VIF:if (optlen != sizeof(vif)) {ret = -EINVAL;break;}if (copy_from_user(&vif, optval, sizeof(vif))) {ret = -EFAULT;break;}if (vif.vifc_vifi >= MAXVIFS) {ret = -ENFILE;break;}if (optname == MRT_ADD_VIF) {ret = vif_add(net, mrt, &vif,sk == rtnl_dereference(mrt->mroute_sk));} else {ret = vif_delete(mrt, vif.vifc_vifi, 0, NULL);}break;/* Manipulate the forwarding caches. These live* in a sort of kernel/user symbiosis.*/case MRT_ADD_MFC:case MRT_DEL_MFC:parent = -1;/* fall through */case MRT_ADD_MFC_PROXY:case MRT_DEL_MFC_PROXY:if (optlen != sizeof(mfc)) {ret = -EINVAL;break;}if (copy_from_user(&mfc, optval, sizeof(mfc))) {ret = -EFAULT;break;}if (parent == 0)parent = mfc.mfcc_parent;if (optname == MRT_DEL_MFC || optname == MRT_DEL_MFC_PROXY)ret = ipmr_mfc_delete(mrt, &mfc, parent);elseret = ipmr_mfc_add(net, mrt, &mfc,sk == rtnl_dereference(mrt->mroute_sk),parent);break;/* Control PIM assert. */case MRT_ASSERT:if (optlen != sizeof(val)) {ret = -EINVAL;break;}if (get_user(val, (int __user *)optval)) {ret = -EFAULT;break;}mrt->mroute_do_assert = val;break;case MRT_PIM:if (!ipmr_pimsm_enabled()) {ret = -ENOPROTOOPT;break;}if (optlen != sizeof(val)) {ret = -EINVAL;break;}if (get_user(val, (int __user *)optval)) {ret = -EFAULT;break;}do_wrvifwhole = (val == IGMPMSG_WRVIFWHOLE);val = !!val;if (val != mrt->mroute_do_pim) {mrt->mroute_do_pim = val;mrt->mroute_do_assert = val;mrt->mroute_do_wrvifwhole = do_wrvifwhole;}break;case MRT_TABLE:if (!IS_BUILTIN(CONFIG_IP_MROUTE_MULTIPLE_TABLES)) {ret = -ENOPROTOOPT;break;}if (optlen != sizeof(uval)) {ret = -EINVAL;break;}if (get_user(uval, (u32 __user *)optval)) {ret = -EFAULT;break;}if (sk == rtnl_dereference(mrt->mroute_sk)) {ret = -EBUSY;} else {mrt = ipmr_new_table(net, uval);if (IS_ERR(mrt))ret = PTR_ERR(mrt);elseraw_sk(sk)->ipmr_table = uval;}break;/* Spurious command, or MRT_VERSION which you cannot set. */default:ret = -ENOPROTOOPT;}
out_unlock:rtnl_unlock();
out:return ret;
}/* Getsock opt support for the multicast routing system. */
int ip_mroute_getsockopt(struct sock *sk, int optname, char __user *optval, int __user *optlen)
{int olr;int val;struct net *net = sock_net(sk);struct mr_table *mrt;if (sk->sk_type != SOCK_RAW ||inet_sk(sk)->inet_num != IPPROTO_IGMP)return -EOPNOTSUPP;mrt = ipmr_get_table(net, raw_sk(sk)->ipmr_table ? : RT_TABLE_DEFAULT);if (!mrt)return -ENOENT;switch (optname) {case MRT_VERSION:val = 0x0305;break;case MRT_PIM:if (!ipmr_pimsm_enabled())return -ENOPROTOOPT;val = mrt->mroute_do_pim;break;case MRT_ASSERT:val = mrt->mroute_do_assert;break;default:return -ENOPROTOOPT;}if (get_user(olr, optlen))return -EFAULT;olr = min_t(unsigned int, olr, sizeof(int));if (olr < 0)return -EINVAL;if (put_user(olr, optlen))return -EFAULT;if (copy_to_user(optval, &val, olr))return -EFAULT;return 0;
}/* The IP multicast ioctl support routines. */
int ipmr_ioctl(struct sock *sk, int cmd, void __user *arg)
{struct sioc_sg_req sr;struct sioc_vif_req vr;struct vif_device *vif;struct mfc_cache *c;struct net *net = sock_net(sk);struct mr_table *mrt;mrt = ipmr_get_table(net, raw_sk(sk)->ipmr_table ? : RT_TABLE_DEFAULT);if (!mrt)return -ENOENT;switch (cmd) {case SIOCGETVIFCNT:if (copy_from_user(&vr, arg, sizeof(vr)))return -EFAULT;if (vr.vifi >= mrt->maxvif)return -EINVAL;vr.vifi = array_index_nospec(vr.vifi, mrt->maxvif);read_lock(&mrt_lock);vif = &mrt->vif_table[vr.vifi];if (VIF_EXISTS(mrt, vr.vifi)) {vr.icount = vif->pkt_in;vr.ocount = vif->pkt_out;vr.ibytes = vif->bytes_in;vr.obytes = vif->bytes_out;read_unlock(&mrt_lock);if (copy_to_user(arg, &vr, sizeof(vr)))return -EFAULT;return 0;}read_unlock(&mrt_lock);return -EADDRNOTAVAIL;case SIOCGETSGCNT:if (copy_from_user(&sr, arg, sizeof(sr)))return -EFAULT;rcu_read_lock();c = ipmr_cache_find(mrt, sr.src.s_addr, sr.grp.s_addr);if (c) {sr.pktcnt = c->_c.mfc_un.res.pkt;sr.bytecnt = c->_c.mfc_un.res.bytes;sr.wrong_if = c->_c.mfc_un.res.wrong_if;rcu_read_unlock();if (copy_to_user(arg, &sr, sizeof(sr)))return -EFAULT;return 0;}rcu_read_unlock();return -EADDRNOTAVAIL;default:return -ENOIOCTLCMD;}
}#ifdef CONFIG_COMPAT
struct compat_sioc_sg_req {struct in_addr src;struct in_addr grp;compat_ulong_t pktcnt;compat_ulong_t bytecnt;compat_ulong_t wrong_if;
};struct compat_sioc_vif_req {vifi_t vifi; /* Which iface */compat_ulong_t icount;compat_ulong_t ocount;compat_ulong_t ibytes;compat_ulong_t obytes;
};int ipmr_compat_ioctl(struct sock *sk, unsigned int cmd, void __user *arg)
{struct compat_sioc_sg_req sr;struct compat_sioc_vif_req vr;struct vif_device *vif;struct mfc_cache *c;struct net *net = sock_net(sk);struct mr_table *mrt;mrt = ipmr_get_table(net, raw_sk(sk)->ipmr_table ? : RT_TABLE_DEFAULT);if (!mrt)return -ENOENT;switch (cmd) {case SIOCGETVIFCNT:if (copy_from_user(&vr, arg, sizeof(vr)))return -EFAULT;if (vr.vifi >= mrt->maxvif)return -EINVAL;vr.vifi = array_index_nospec(vr.vifi, mrt->maxvif);read_lock(&mrt_lock);vif = &mrt->vif_table[vr.vifi];if (VIF_EXISTS(mrt, vr.vifi)) {vr.icount = vif->pkt_in;vr.ocount = vif->pkt_out;vr.ibytes = vif->bytes_in;vr.obytes = vif->bytes_out;read_unlock(&mrt_lock);if (copy_to_user(arg, &vr, sizeof(vr)))return -EFAULT;return 0;}read_unlock(&mrt_lock);return -EADDRNOTAVAIL;case SIOCGETSGCNT:if (copy_from_user(&sr, arg, sizeof(sr)))return -EFAULT;rcu_read_lock();c = ipmr_cache_find(mrt, sr.src.s_addr, sr.grp.s_addr);if (c) {sr.pktcnt = c->_c.mfc_un.res.pkt;sr.bytecnt = c->_c.mfc_un.res.bytes;sr.wrong_if = c->_c.mfc_un.res.wrong_if;rcu_read_unlock();if (copy_to_user(arg, &sr, sizeof(sr)))return -EFAULT;return 0;}rcu_read_unlock();return -EADDRNOTAVAIL;default:return -ENOIOCTLCMD;}
}
#endifstatic int ipmr_device_event(struct notifier_block *this, unsigned long event, void *ptr)
{struct net_device *dev = netdev_notifier_info_to_dev(ptr);struct net *net = dev_net(dev);struct mr_table *mrt;struct vif_device *v;int ct;if (event != NETDEV_UNREGISTER)return NOTIFY_DONE;ipmr_for_each_table(mrt, net) {v = &mrt->vif_table[0];for (ct = 0; ct < mrt->maxvif; ct++, v++) {if (v->dev == dev)vif_delete(mrt, ct, 1, NULL);}}return NOTIFY_DONE;
}static struct notifier_block ip_mr_notifier = {.notifier_call = ipmr_device_event,
};/* Encapsulate a packet by attaching a valid IPIP header to it.* This avoids tunnel drivers and other mess and gives us the speed so* important for multicast video.*/
static void ip_encap(struct net *net, struct sk_buff *skb,__be32 saddr, __be32 daddr)
{struct iphdr *iph;const struct iphdr *old_iph = ip_hdr(skb);skb_push(skb, sizeof(struct iphdr));skb->transport_header = skb->network_header;skb_reset_network_header(skb);iph = ip_hdr(skb);iph->version = 4;iph->tos = old_iph->tos;iph->ttl = old_iph->ttl;iph->frag_off = 0;iph->daddr = daddr;iph->saddr = saddr;iph->protocol = IPPROTO_IPIP;iph->ihl = 5;iph->tot_len = htons(skb->len);ip_select_ident(net, skb, NULL);ip_send_check(iph);memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));nf_reset(skb);
}static inline int ipmr_forward_finish(struct net *net, struct sock *sk,struct sk_buff *skb)
{struct ip_options *opt = &(IPCB(skb)->opt);IP_INC_STATS(net, IPSTATS_MIB_OUTFORWDATAGRAMS);IP_ADD_STATS(net, IPSTATS_MIB_OUTOCTETS, skb->len);if (unlikely(opt->optlen))ip_forward_options(skb);return dst_output(net, sk, skb);
}#ifdef CONFIG_NET_SWITCHDEV
static bool ipmr_forward_offloaded(struct sk_buff *skb, struct mr_table *mrt,int in_vifi, int out_vifi)
{struct vif_device *out_vif = &mrt->vif_table[out_vifi];struct vif_device *in_vif = &mrt->vif_table[in_vifi];if (!skb->offload_mr_fwd_mark)return false;if (!out_vif->dev_parent_id.id_len || !in_vif->dev_parent_id.id_len)return false;return netdev_phys_item_id_same(&out_vif->dev_parent_id,&in_vif->dev_parent_id);
}
#else
static bool ipmr_forward_offloaded(struct sk_buff *skb, struct mr_table *mrt,int in_vifi, int out_vifi)
{return false;
}
#endif/* Processing handlers for ipmr_forward */static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt,int in_vifi, struct sk_buff *skb,struct mfc_cache *c, int vifi)
{const struct iphdr *iph = ip_hdr(skb);struct vif_device *vif = &mrt->vif_table[vifi];struct net_device *dev;struct rtable *rt;struct flowi4 fl4;int encap = 0;if (!vif->dev)goto out_free;if (vif->flags & VIFF_REGISTER) {vif->pkt_out++;vif->bytes_out += skb->len;vif->dev->stats.tx_bytes += skb->len;vif->dev->stats.tx_packets++;ipmr_cache_report(mrt, skb, vifi, IGMPMSG_WHOLEPKT);goto out_free;}if (ipmr_forward_offloaded(skb, mrt, in_vifi, vifi))goto out_free;if (vif->flags & VIFF_TUNNEL) {rt = ip_route_output_ports(net, &fl4, NULL,vif->remote, vif->local,0, 0,IPPROTO_IPIP,RT_TOS(iph->tos), vif->link);if (IS_ERR(rt))goto out_free;encap = sizeof(struct iphdr);} else {rt = ip_route_output_ports(net, &fl4, NULL, iph->daddr, 0,0, 0,IPPROTO_IPIP,RT_TOS(iph->tos), vif->link);if (IS_ERR(rt))goto out_free;}dev = rt->dst.dev;if (skb->len+encap > dst_mtu(&rt->dst) && (ntohs(iph->frag_off) & IP_DF)) {/* Do not fragment multicasts. Alas, IPv4 does not* allow to send ICMP, so that packets will disappear* to blackhole.*/IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);ip_rt_put(rt);goto out_free;}encap += LL_RESERVED_SPACE(dev) + rt->dst.header_len;if (skb_cow(skb, encap)) {ip_rt_put(rt);goto out_free;}vif->pkt_out++;vif->bytes_out += skb->len;skb_dst_drop(skb);skb_dst_set(skb, &rt->dst);ip_decrease_ttl(ip_hdr(skb));/* FIXME: forward and output firewalls used to be called here.* What do we do with netfilter? -- RR*/if (vif->flags & VIFF_TUNNEL) {ip_encap(net, skb, vif->local, vif->remote);/* FIXME: extra output firewall step used to be here. --RR */vif->dev->stats.tx_packets++;vif->dev->stats.tx_bytes += skb->len;}IPCB(skb)->flags |= IPSKB_FORWARDED;/* RFC1584 teaches, that DVMRP/PIM router must deliver packets locally* not only before forwarding, but after forwarding on all output* interfaces. It is clear, if mrouter runs a multicasting* program, it should receive packets not depending to what interface* program is joined.* If we will not make it, the program will have to join on all* interfaces. On the other hand, multihoming host (or router, but* not mrouter) cannot join to more than one interface - it will* result in receiving multiple packets.*/NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD,net, NULL, skb, skb->dev, dev,ipmr_forward_finish);return;out_free:kfree_skb(skb);
}static int ipmr_find_vif(struct mr_table *mrt, struct net_device *dev)
{int ct;for (ct = mrt->maxvif-1; ct >= 0; ct--) {if (mrt->vif_table[ct].dev == dev)break;}return ct;
}/* "local" means that we should preserve one skb (for local delivery) */
static void ip_mr_forward(struct net *net, struct mr_table *mrt,struct net_device *dev, struct sk_buff *skb,struct mfc_cache *c, int local)
{int true_vifi = ipmr_find_vif(mrt, dev);int psend = -1;int vif, ct;vif = c->_c.mfc_parent;c->_c.mfc_un.res.pkt++;c->_c.mfc_un.res.bytes += skb->len;c->_c.mfc_un.res.lastuse = jiffies;if (c->mfc_origin == htonl(INADDR_ANY) && true_vifi >= 0) {struct mfc_cache *cache_proxy;/* For an (*,G) entry, we only check that the incomming* interface is part of the static tree.*/cache_proxy = mr_mfc_find_any_parent(mrt, vif);if (cache_proxy &&cache_proxy->_c.mfc_un.res.ttls[true_vifi] < 255)goto forward;}/* Wrong interface: drop packet and (maybe) send PIM assert. */if (mrt->vif_table[vif].dev != dev) {if (rt_is_output_route(skb_rtable(skb))) {/* It is our own packet, looped back.* Very complicated situation...** The best workaround until routing daemons will be* fixed is not to redistribute packet, if it was* send through wrong interface. It means, that* multicast applications WILL NOT work for* (S,G), which have default multicast route pointing* to wrong oif. In any case, it is not a good* idea to use multicasting applications on router.*/goto dont_forward;}c->_c.mfc_un.res.wrong_if++;if (true_vifi >= 0 && mrt->mroute_do_assert &&/* pimsm uses asserts, when switching from RPT to SPT,* so that we cannot check that packet arrived on an oif.* It is bad, but otherwise we would need to move pretty* large chunk of pimd to kernel. Ough... --ANK*/(mrt->mroute_do_pim ||c->_c.mfc_un.res.ttls[true_vifi] < 255) &&time_after(jiffies,c->_c.mfc_un.res.last_assert +MFC_ASSERT_THRESH)) {c->_c.mfc_un.res.last_assert = jiffies;ipmr_cache_report(mrt, skb, true_vifi, IGMPMSG_WRONGVIF);if (mrt->mroute_do_wrvifwhole)ipmr_cache_report(mrt, skb, true_vifi,IGMPMSG_WRVIFWHOLE);}goto dont_forward;}forward:mrt->vif_table[vif].pkt_in++;mrt->vif_table[vif].bytes_in += skb->len;/* Forward the frame */if (c->mfc_origin == htonl(INADDR_ANY) &&c->mfc_mcastgrp == htonl(INADDR_ANY)) {if (true_vifi >= 0 &&true_vifi != c->_c.mfc_parent &&ip_hdr(skb)->ttl >c->_c.mfc_un.res.ttls[c->_c.mfc_parent]) {/* It's an (*,*) entry and the packet is not coming from* the upstream: forward the packet to the upstream* only.*/psend = c->_c.mfc_parent;goto last_forward;}goto dont_forward;}for (ct = c->_c.mfc_un.res.maxvif - 1;ct >= c->_c.mfc_un.res.minvif; ct--) {/* For (*,G) entry, don't forward to the incoming interface */if ((c->mfc_origin != htonl(INADDR_ANY) ||ct != true_vifi) &&ip_hdr(skb)->ttl > c->_c.mfc_un.res.ttls[ct]) {if (psend != -1) {struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);if (skb2)ipmr_queue_xmit(net, mrt, true_vifi,skb2, c, psend);}psend = ct;}}
last_forward:if (psend != -1) {if (local) {struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);if (skb2)ipmr_queue_xmit(net, mrt, true_vifi, skb2,c, psend);} else {ipmr_queue_xmit(net, mrt, true_vifi, skb, c, psend);return;}}dont_forward:if (!local)kfree_skb(skb);
}static struct mr_table *ipmr_rt_fib_lookup(struct net *net, struct sk_buff *skb)
{struct rtable *rt = skb_rtable(skb);struct iphdr *iph = ip_hdr(skb);struct flowi4 fl4 = {.daddr = iph->daddr,.saddr = iph->saddr,.flowi4_tos = RT_TOS(iph->tos),.flowi4_oif = (rt_is_output_route(rt) ?skb->dev->ifindex : 0),.flowi4_iif = (rt_is_output_route(rt) ?LOOPBACK_IFINDEX :skb->dev->ifindex),.flowi4_mark = skb->mark,};struct mr_table *mrt;int err;err = ipmr_fib_lookup(net, &fl4, &mrt);if (err)return ERR_PTR(err);return mrt;
}/* Multicast packets for forwarding arrive here* Called with rcu_read_lock();*/
int ip_mr_input(struct sk_buff *skb)
{struct mfc_cache *cache;struct net *net = dev_net(skb->dev);int local = skb_rtable(skb)->rt_flags & RTCF_LOCAL;struct mr_table *mrt;struct net_device *dev;/* skb->dev passed in is the loX master dev for vrfs.* As there are no vifs associated with loopback devices,* get the proper interface that does have a vif associated with it.*/dev = skb->dev;if (netif_is_l3_master(skb->dev)) {dev = dev_get_by_index_rcu(net, IPCB(skb)->iif);if (!dev) {kfree_skb(skb);return -ENODEV;}}/* Packet is looped back after forward, it should not be* forwarded second time, but still can be delivered locally.*/if (IPCB(skb)->flags & IPSKB_FORWARDED)goto dont_forward;mrt = ipmr_rt_fib_lookup(net, skb);if (IS_ERR(mrt)) {kfree_skb(skb);return PTR_ERR(mrt);}if (!local) {if (IPCB(skb)->opt.router_alert) {if (ip_call_ra_chain(skb))return 0;} else if (ip_hdr(skb)->protocol == IPPROTO_IGMP) {/* IGMPv1 (and broken IGMPv2 implementations sort of* Cisco IOS <= 11.2(8)) do not put router alert* option to IGMP packets destined to routable* groups. It is very bad, because it means* that we can forward NO IGMP messages.*/struct sock *mroute_sk;mroute_sk = rcu_dereference(mrt->mroute_sk);if (mroute_sk) {nf_reset(skb);raw_rcv(mroute_sk, skb);return 0;}}}/* already under rcu_read_lock() */cache = ipmr_cache_find(mrt, ip_hdr(skb)->saddr, ip_hdr(skb)->daddr);if (!cache) {int vif = ipmr_find_vif(mrt, dev);if (vif >= 0)cache = ipmr_cache_find_any(mrt, ip_hdr(skb)->daddr,vif);}/* No usable cache entry */if (!cache) {int vif;if (local) {struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);ip_local_deliver(skb);if (!skb2)return -ENOBUFS;skb = skb2;}read_lock(&mrt_lock);vif = ipmr_find_vif(mrt, dev);if (vif >= 0) {int err2 = ipmr_cache_unresolved(mrt, vif, skb, dev);read_unlock(&mrt_lock);return err2;}read_unlock(&mrt_lock);kfree_skb(skb);return -ENODEV;}read_lock(&mrt_lock);ip_mr_forward(net, mrt, dev, skb, cache, local);read_unlock(&mrt_lock);if (local)return ip_local_deliver(skb);return 0;dont_forward:if (local)return ip_local_deliver(skb);kfree_skb(skb);return 0;
}#ifdef CONFIG_IP_PIMSM_V1
/* Handle IGMP messages of PIMv1 */
int pim_rcv_v1(struct sk_buff *skb)
{struct igmphdr *pim;struct net *net = dev_net(skb->dev);struct mr_table *mrt;if (!pskb_may_pull(skb, sizeof(*pim) + sizeof(struct iphdr)))goto drop;pim = igmp_hdr(skb);mrt = ipmr_rt_fib_lookup(net, skb);if (IS_ERR(mrt))goto drop;if (!mrt->mroute_do_pim ||pim->group != PIM_V1_VERSION || pim->code != PIM_V1_REGISTER)goto drop;if (__pim_rcv(mrt, skb, sizeof(*pim))) {
drop:kfree_skb(skb);}return 0;
}
#endif#ifdef CONFIG_IP_PIMSM_V2
static int pim_rcv(struct sk_buff *skb)
{struct pimreghdr *pim;struct net *net = dev_net(skb->dev);struct mr_table *mrt;if (!pskb_may_pull(skb, sizeof(*pim) + sizeof(struct iphdr)))goto drop;pim = (struct pimreghdr *)skb_transport_header(skb);if (pim->type != ((PIM_VERSION << 4) | (PIM_TYPE_REGISTER)) ||(pim->flags & PIM_NULL_REGISTER) ||(ip_compute_csum((void *)pim, sizeof(*pim)) != 0 &&csum_fold(skb_checksum(skb, 0, skb->len, 0))))goto drop;mrt = ipmr_rt_fib_lookup(net, skb);if (IS_ERR(mrt))goto drop;if (__pim_rcv(mrt, skb, sizeof(*pim))) {
drop:kfree_skb(skb);}return 0;
}
#endifint ipmr_get_route(struct net *net, struct sk_buff *skb,__be32 saddr, __be32 daddr,struct rtmsg *rtm, u32 portid)
{struct mfc_cache *cache;struct mr_table *mrt;int err;mrt = ipmr_get_table(net, RT_TABLE_DEFAULT);if (!mrt)return -ENOENT;rcu_read_lock();cache = ipmr_cache_find(mrt, saddr, daddr);if (!cache && skb->dev) {int vif = ipmr_find_vif(mrt, skb->dev);if (vif >= 0)cache = ipmr_cache_find_any(mrt, daddr, vif);}if (!cache) {struct sk_buff *skb2;struct iphdr *iph;struct net_device *dev;int vif = -1;dev = skb->dev;read_lock(&mrt_lock);if (dev)vif = ipmr_find_vif(mrt, dev);if (vif < 0) {read_unlock(&mrt_lock);rcu_read_unlock();return -ENODEV;}skb2 = skb_clone(skb, GFP_ATOMIC);if (!skb2) {read_unlock(&mrt_lock);rcu_read_unlock();return -ENOMEM;}NETLINK_CB(skb2).portid = portid;skb_push(skb2, sizeof(struct iphdr));skb_reset_network_header(skb2);iph = ip_hdr(skb2);iph->ihl = sizeof(struct iphdr) >> 2;iph->saddr = saddr;iph->daddr = daddr;iph->version = 0;err = ipmr_cache_unresolved(mrt, vif, skb2, dev);read_unlock(&mrt_lock);rcu_read_unlock();return err;}read_lock(&mrt_lock);err = mr_fill_mroute(mrt, skb, &cache->_c, rtm);read_unlock(&mrt_lock);rcu_read_unlock();return err;
}static int ipmr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,u32 portid, u32 seq, struct mfc_cache *c, int cmd,int flags)
{struct nlmsghdr *nlh;struct rtmsg *rtm;int err;nlh = nlmsg_put(skb, portid, seq, cmd, sizeof(*rtm), flags);if (!nlh)return -EMSGSIZE;rtm = nlmsg_data(nlh);rtm->rtm_family = RTNL_FAMILY_IPMR;rtm->rtm_dst_len = 32;rtm->rtm_src_len = 32;rtm->rtm_tos = 0;rtm->rtm_table = mrt->id;if (nla_put_u32(skb, RTA_TABLE, mrt->id))goto nla_put_failure;rtm->rtm_type = RTN_MULTICAST;rtm->rtm_scope = RT_SCOPE_UNIVERSE;if (c->_c.mfc_flags & MFC_STATIC)rtm->rtm_protocol = RTPROT_STATIC;elsertm->rtm_protocol = RTPROT_MROUTED;rtm->rtm_flags = 0;if (nla_put_in_addr(skb, RTA_SRC, c->mfc_origin) ||nla_put_in_addr(skb, RTA_DST, c->mfc_mcastgrp))goto nla_put_failure;err = mr_fill_mroute(mrt, skb, &c->_c, rtm);/* do not break the dump if cache is unresolved */if (err < 0 && err != -ENOENT)goto nla_put_failure;nlmsg_end(skb, nlh);return 0;nla_put_failure:nlmsg_cancel(skb, nlh);return -EMSGSIZE;
}static int _ipmr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,u32 portid, u32 seq, struct mr_mfc *c, int cmd,int flags)
{return ipmr_fill_mroute(mrt, skb, portid, seq, (struct mfc_cache *)c,cmd, flags);
}static size_t mroute_msgsize(bool unresolved, int maxvif)
{size_t len =NLMSG_ALIGN(sizeof(struct rtmsg))+ nla_total_size(4) /* RTA_TABLE */+ nla_total_size(4) /* RTA_SRC */+ nla_total_size(4) /* RTA_DST */;if (!unresolved)len = len+ nla_total_size(4) /* RTA_IIF */+ nla_total_size(0) /* RTA_MULTIPATH */+ maxvif * NLA_ALIGN(sizeof(struct rtnexthop))/* RTA_MFC_STATS */+ nla_total_size_64bit(sizeof(struct rta_mfc_stats));return len;
}static void mroute_netlink_event(struct mr_table *mrt, struct mfc_cache *mfc,int cmd)
{struct net *net = read_pnet(&mrt->net);struct sk_buff *skb;int err = -ENOBUFS;skb = nlmsg_new(mroute_msgsize(mfc->_c.mfc_parent >= MAXVIFS,mrt->maxvif),GFP_ATOMIC);if (!skb)goto errout;err = ipmr_fill_mroute(mrt, skb, 0, 0, mfc, cmd, 0);if (err < 0)goto errout;rtnl_notify(skb, net, 0, RTNLGRP_IPV4_MROUTE, NULL, GFP_ATOMIC);return;errout:kfree_skb(skb);if (err < 0)rtnl_set_sk_err(net, RTNLGRP_IPV4_MROUTE, err);
}static size_t igmpmsg_netlink_msgsize(size_t payloadlen)
{size_t len =NLMSG_ALIGN(sizeof(struct rtgenmsg))+ nla_total_size(1) /* IPMRA_CREPORT_MSGTYPE */+ nla_total_size(4) /* IPMRA_CREPORT_VIF_ID */+ nla_total_size(4) /* IPMRA_CREPORT_SRC_ADDR */+ nla_total_size(4) /* IPMRA_CREPORT_DST_ADDR *//* IPMRA_CREPORT_PKT */+ nla_total_size(payloadlen);return len;
}static void igmpmsg_netlink_event(struct mr_table *mrt, struct sk_buff *pkt)
{struct net *net = read_pnet(&mrt->net);struct nlmsghdr *nlh;struct rtgenmsg *rtgenm;struct igmpmsg *msg;struct sk_buff *skb;struct nlattr *nla;int payloadlen;payloadlen = pkt->len - sizeof(struct igmpmsg);msg = (struct igmpmsg *)skb_network_header(pkt);skb = nlmsg_new(igmpmsg_netlink_msgsize(payloadlen), GFP_ATOMIC);if (!skb)goto errout;nlh = nlmsg_put(skb, 0, 0, RTM_NEWCACHEREPORT,sizeof(struct rtgenmsg), 0);if (!nlh)goto errout;rtgenm = nlmsg_data(nlh);rtgenm->rtgen_family = RTNL_FAMILY_IPMR;if (nla_put_u8(skb, IPMRA_CREPORT_MSGTYPE, msg->im_msgtype) ||nla_put_u32(skb, IPMRA_CREPORT_VIF_ID, msg->im_vif) ||nla_put_in_addr(skb, IPMRA_CREPORT_SRC_ADDR,msg->im_src.s_addr) ||nla_put_in_addr(skb, IPMRA_CREPORT_DST_ADDR,msg->im_dst.s_addr))goto nla_put_failure;nla = nla_reserve(skb, IPMRA_CREPORT_PKT, payloadlen);if (!nla || skb_copy_bits(pkt, sizeof(struct igmpmsg),nla_data(nla), payloadlen))goto nla_put_failure;nlmsg_end(skb, nlh);rtnl_notify(skb, net, 0, RTNLGRP_IPV4_MROUTE_R, NULL, GFP_ATOMIC);return;nla_put_failure:nlmsg_cancel(skb, nlh);
errout:kfree_skb(skb);rtnl_set_sk_err(net, RTNLGRP_IPV4_MROUTE_R, -ENOBUFS);
}static int ipmr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,struct netlink_ext_ack *extack)
{struct net *net = sock_net(in_skb->sk);struct nlattr *tb[RTA_MAX + 1];struct sk_buff *skb = NULL;struct mfc_cache *cache;struct mr_table *mrt;struct rtmsg *rtm;__be32 src, grp;u32 tableid;int err;err = nlmsg_parse(nlh, sizeof(*rtm), tb, RTA_MAX,rtm_ipv4_policy, extack);if (err < 0)goto errout;rtm = nlmsg_data(nlh);src = tb[RTA_SRC] ? nla_get_in_addr(tb[RTA_SRC]) : 0;grp = tb[RTA_DST] ? nla_get_in_addr(tb[RTA_DST]) : 0;tableid = tb[RTA_TABLE] ? nla_get_u32(tb[RTA_TABLE]) : 0;mrt = ipmr_get_table(net, tableid ? tableid : RT_TABLE_DEFAULT);if (!mrt) {err = -ENOENT;goto errout_free;}/* entries are added/deleted only under RTNL */rcu_read_lock();cache = ipmr_cache_find(mrt, src, grp);rcu_read_unlock();if (!cache) {err = -ENOENT;goto errout_free;}skb = nlmsg_new(mroute_msgsize(false, mrt->maxvif), GFP_KERNEL);if (!skb) {err = -ENOBUFS;goto errout_free;}err = ipmr_fill_mroute(mrt, skb, NETLINK_CB(in_skb).portid,nlh->nlmsg_seq, cache,RTM_NEWROUTE, 0);if (err < 0)goto errout_free;err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);errout:return err;errout_free:kfree_skb(skb);goto errout;
}static int ipmr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb)
{return mr_rtm_dumproute(skb, cb, ipmr_mr_table_iter,_ipmr_fill_mroute, &mfc_unres_lock);
}static const struct nla_policy rtm_ipmr_policy[RTA_MAX + 1] = {[RTA_SRC] = { .type = NLA_U32 },[RTA_DST] = { .type = NLA_U32 },[RTA_IIF] = { .type = NLA_U32 },[RTA_TABLE] = { .type = NLA_U32 },[RTA_MULTIPATH] = { .len = sizeof(struct rtnexthop) },
};static bool ipmr_rtm_validate_proto(unsigned char rtm_protocol)
{switch (rtm_protocol) {case RTPROT_STATIC:case RTPROT_MROUTED:return true;}return false;
}static int ipmr_nla_get_ttls(const struct nlattr *nla, struct mfcctl *mfcc)
{struct rtnexthop *rtnh = nla_data(nla);int remaining = nla_len(nla), vifi = 0;while (rtnh_ok(rtnh, remaining)) {mfcc->mfcc_ttls[vifi] = rtnh->rtnh_hops;if (++vifi == MAXVIFS)break;rtnh = rtnh_next(rtnh, &remaining);}return remaining > 0 ? -EINVAL : vifi;
}/* returns < 0 on error, 0 for ADD_MFC and 1 for ADD_MFC_PROXY */
static int rtm_to_ipmr_mfcc(struct net *net, struct nlmsghdr *nlh,struct mfcctl *mfcc, int *mrtsock,struct mr_table **mrtret,struct netlink_ext_ack *extack)
{struct net_device *dev = NULL;u32 tblid = RT_TABLE_DEFAULT;struct mr_table *mrt;struct nlattr *attr;struct rtmsg *rtm;int ret, rem;ret = nlmsg_validate(nlh, sizeof(*rtm), RTA_MAX, rtm_ipmr_policy,extack);if (ret < 0)goto out;rtm = nlmsg_data(nlh);ret = -EINVAL;if (rtm->rtm_family != RTNL_FAMILY_IPMR || rtm->rtm_dst_len != 32 ||rtm->rtm_type != RTN_MULTICAST ||rtm->rtm_scope != RT_SCOPE_UNIVERSE ||!ipmr_rtm_validate_proto(rtm->rtm_protocol))goto out;memset(mfcc, 0, sizeof(*mfcc));mfcc->mfcc_parent = -1;ret = 0;nlmsg_for_each_attr(attr, nlh, sizeof(struct rtmsg), rem) {switch (nla_type(attr)) {case RTA_SRC:mfcc->mfcc_origin.s_addr = nla_get_be32(attr);break;case RTA_DST:mfcc->mfcc_mcastgrp.s_addr = nla_get_be32(attr);break;case RTA_IIF:dev = __dev_get_by_index(net, nla_get_u32(attr));if (!dev) {ret = -ENODEV;goto out;}break;case RTA_MULTIPATH:if (ipmr_nla_get_ttls(attr, mfcc) < 0) {ret = -EINVAL;goto out;}break;case RTA_PREFSRC:ret = 1;break;case RTA_TABLE:tblid = nla_get_u32(attr);break;}}mrt = ipmr_get_table(net, tblid);if (!mrt) {ret = -ENOENT;goto out;}*mrtret = mrt;*mrtsock = rtm->rtm_protocol == RTPROT_MROUTED ? 1 : 0;if (dev)mfcc->mfcc_parent = ipmr_find_vif(mrt, dev);out:return ret;
}/* takes care of both newroute and delroute */
static int ipmr_rtm_route(struct sk_buff *skb, struct nlmsghdr *nlh,struct netlink_ext_ack *extack)
{struct net *net = sock_net(skb->sk);int ret, mrtsock, parent;struct mr_table *tbl;struct mfcctl mfcc;mrtsock = 0;tbl = NULL;ret = rtm_to_ipmr_mfcc(net, nlh, &mfcc, &mrtsock, &tbl, extack);if (ret < 0)return ret;parent = ret ? mfcc.mfcc_parent : -1;if (nlh->nlmsg_type == RTM_NEWROUTE)return ipmr_mfc_add(net, tbl, &mfcc, mrtsock, parent);elsereturn ipmr_mfc_delete(tbl, &mfcc, parent);
}static bool ipmr_fill_table(struct mr_table *mrt, struct sk_buff *skb)
{u32 queue_len = atomic_read(&mrt->cache_resolve_queue_len);if (nla_put_u32(skb, IPMRA_TABLE_ID, mrt->id) ||nla_put_u32(skb, IPMRA_TABLE_CACHE_RES_QUEUE_LEN, queue_len) ||nla_put_s32(skb, IPMRA_TABLE_MROUTE_REG_VIF_NUM,mrt->mroute_reg_vif_num) ||nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_ASSERT,mrt->mroute_do_assert) ||nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_PIM, mrt->mroute_do_pim) ||nla_put_u8(skb, IPMRA_TABLE_MROUTE_DO_WRVIFWHOLE,mrt->mroute_do_wrvifwhole))return false;return true;
}static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb)
{struct nlattr *vif_nest;struct vif_device *vif;/* if the VIF doesn't exist just continue */if (!VIF_EXISTS(mrt, vifid))return true;vif = &mrt->vif_table[vifid];vif_nest = nla_nest_start(skb, IPMRA_VIF);if (!vif_nest)return false;if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, vif->dev->ifindex) ||nla_put_u32(skb, IPMRA_VIFA_VIF_ID, vifid) ||nla_put_u16(skb, IPMRA_VIFA_FLAGS, vif->flags) ||nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_IN, vif->bytes_in,IPMRA_VIFA_PAD) ||nla_put_u64_64bit(skb, IPMRA_VIFA_BYTES_OUT, vif->bytes_out,IPMRA_VIFA_PAD) ||nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_IN, vif->pkt_in,IPMRA_VIFA_PAD) ||nla_put_u64_64bit(skb, IPMRA_VIFA_PACKETS_OUT, vif->pkt_out,IPMRA_VIFA_PAD) ||nla_put_be32(skb, IPMRA_VIFA_LOCAL_ADDR, vif->local) ||nla_put_be32(skb, IPMRA_VIFA_REMOTE_ADDR, vif->remote)) {nla_nest_cancel(skb, vif_nest);return false;}nla_nest_end(skb, vif_nest);return true;
}static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb)
{struct net *net = sock_net(skb->sk);struct nlmsghdr *nlh = NULL;unsigned int t = 0, s_t;unsigned int e = 0, s_e;struct mr_table *mrt;s_t = cb->args[0];s_e = cb->args[1];ipmr_for_each_table(mrt, net) {struct nlattr *vifs, *af;struct ifinfomsg *hdr;u32 i;if (t < s_t)goto skip_table;nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid,cb->nlh->nlmsg_seq, RTM_NEWLINK,sizeof(*hdr), NLM_F_MULTI);if (!nlh)break;hdr = nlmsg_data(nlh);memset(hdr, 0, sizeof(*hdr));hdr->ifi_family = RTNL_FAMILY_IPMR;af = nla_nest_start(skb, IFLA_AF_SPEC);if (!af) {nlmsg_cancel(skb, nlh);goto out;}if (!ipmr_fill_table(mrt, skb)) {nlmsg_cancel(skb, nlh);goto out;}vifs = nla_nest_start(skb, IPMRA_TABLE_VIFS);if (!vifs) {nla_nest_end(skb, af);nlmsg_end(skb, nlh);goto out;}for (i = 0; i < mrt->maxvif; i++) {if (e < s_e)goto skip_entry;if (!ipmr_fill_vif(mrt, i, skb)) {nla_nest_end(skb, vifs);nla_nest_end(skb, af);nlmsg_end(skb, nlh);goto out;}
skip_entry:e++;}s_e = 0;e = 0;nla_nest_end(skb, vifs);nla_nest_end(skb, af);nlmsg_end(skb, nlh);
skip_table:t++;}out:cb->args[1] = e;cb->args[0] = t;return skb->len;
}#ifdef CONFIG_PROC_FS
/* The /proc interfaces to multicast routing :* /proc/net/ip_mr_cache & /proc/net/ip_mr_vif*/static void *ipmr_vif_seq_start(struct seq_file *seq, loff_t *pos)__acquires(mrt_lock)
{struct mr_vif_iter *iter = seq->private;struct net *net = seq_file_net(seq);struct mr_table *mrt;mrt = ipmr_get_table(net, RT_TABLE_DEFAULT);if (!mrt)return ERR_PTR(-ENOENT);iter->mrt = mrt;read_lock(&mrt_lock);return mr_vif_seq_start(seq, pos);
}static void ipmr_vif_seq_stop(struct seq_file *seq, void *v)__releases(mrt_lock)
{read_unlock(&mrt_lock);
}static int ipmr_vif_seq_show(struct seq_file *seq, void *v)
{struct mr_vif_iter *iter = seq->private;struct mr_table *mrt = iter->mrt;if (v == SEQ_START_TOKEN) {seq_puts(seq,"Interface BytesIn PktsIn BytesOut PktsOut Flags Local Remote\n");} else {const struct vif_device *vif = v;const char *name = vif->dev ?vif->dev->name : "none";seq_printf(seq,"%2td %-10s %8ld %7ld %8ld %7ld %05X %08X %08X\n",vif - mrt->vif_table,name, vif->bytes_in, vif->pkt_in,vif->bytes_out, vif->pkt_out,vif->flags, vif->local, vif->remote);}return 0;
}static const struct seq_operations ipmr_vif_seq_ops = {.start = ipmr_vif_seq_start,.next = mr_vif_seq_next,.stop = ipmr_vif_seq_stop,.show = ipmr_vif_seq_show,
};static void *ipmr_mfc_seq_start(struct seq_file *seq, loff_t *pos)
{struct net *net = seq_file_net(seq);struct mr_table *mrt;mrt = ipmr_get_table(net, RT_TABLE_DEFAULT);if (!mrt)return ERR_PTR(-ENOENT);return mr_mfc_seq_start(seq, pos, mrt, &mfc_unres_lock);
}static int ipmr_mfc_seq_show(struct seq_file *seq, void *v)
{int n;if (v == SEQ_START_TOKEN) {seq_puts(seq,"Group Origin Iif Pkts Bytes Wrong Oifs\n");} else {const struct mfc_cache *mfc = v;const struct mr_mfc_iter *it = seq->private;const struct mr_table *mrt = it->mrt;seq_printf(seq, "%08X %08X %-3hd",(__force u32) mfc->mfc_mcastgrp,(__force u32) mfc->mfc_origin,mfc->_c.mfc_parent);if (it->cache != &mrt->mfc_unres_queue) {seq_printf(seq, " %8lu %8lu %8lu",mfc->_c.mfc_un.res.pkt,mfc->_c.mfc_un.res.bytes,mfc->_c.mfc_un.res.wrong_if);for (n = mfc->_c.mfc_un.res.minvif;n < mfc->_c.mfc_un.res.maxvif; n++) {if (VIF_EXISTS(mrt, n) &&mfc->_c.mfc_un.res.ttls[n] < 255)seq_printf(seq," %2d:%-3d",n, mfc->_c.mfc_un.res.ttls[n]);}} else {/* unresolved mfc_caches don't contain* pkt, bytes and wrong_if values*/seq_printf(seq, " %8lu %8lu %8lu", 0ul, 0ul, 0ul);}seq_putc(seq, '\n');}return 0;
}static const struct seq_operations ipmr_mfc_seq_ops = {.start = ipmr_mfc_seq_start,.next = mr_mfc_seq_next,.stop = mr_mfc_seq_stop,.show = ipmr_mfc_seq_show,
};
#endif#ifdef CONFIG_IP_PIMSM_V2
static const struct net_protocol pim_protocol = {.handler = pim_rcv,.netns_ok = 1,
};
#endifstatic unsigned int ipmr_seq_read(struct net *net)
{ASSERT_RTNL();return net->ipv4.ipmr_seq + ipmr_rules_seq_read(net);
}static int ipmr_dump(struct net *net, struct notifier_block *nb)
{return mr_dump(net, nb, RTNL_FAMILY_IPMR, ipmr_rules_dump,ipmr_mr_table_iter, &mrt_lock);
}static const struct fib_notifier_ops ipmr_notifier_ops_template = {.family = RTNL_FAMILY_IPMR,.fib_seq_read = ipmr_seq_read,.fib_dump = ipmr_dump,.owner = THIS_MODULE,
};static int __net_init ipmr_notifier_init(struct net *net)
{struct fib_notifier_ops *ops;net->ipv4.ipmr_seq = 0;ops = fib_notifier_ops_register(&ipmr_notifier_ops_template, net);if (IS_ERR(ops))return PTR_ERR(ops);net->ipv4.ipmr_notifier_ops = ops;return 0;
}static void __net_exit ipmr_notifier_exit(struct net *net)
{fib_notifier_ops_unregister(net->ipv4.ipmr_notifier_ops);net->ipv4.ipmr_notifier_ops = NULL;
}/* Setup for IP multicast routing */
static int __net_init ipmr_net_init(struct net *net)
{int err;err = ipmr_notifier_init(net);if (err)goto ipmr_notifier_fail;err = ipmr_rules_init(net);if (err < 0)goto ipmr_rules_fail;#ifdef CONFIG_PROC_FSerr = -ENOMEM;if (!proc_create_net("ip_mr_vif", 0, net->proc_net, &ipmr_vif_seq_ops,sizeof(struct mr_vif_iter)))goto proc_vif_fail;if (!proc_create_net("ip_mr_cache", 0, net->proc_net, &ipmr_mfc_seq_ops,sizeof(struct mr_mfc_iter)))goto proc_cache_fail;
#endifreturn 0;#ifdef CONFIG_PROC_FS
proc_cache_fail:remove_proc_entry("ip_mr_vif", net->proc_net);
proc_vif_fail:ipmr_rules_exit(net);
#endif
ipmr_rules_fail:ipmr_notifier_exit(net);
ipmr_notifier_fail:return err;
}static void __net_exit ipmr_net_exit(struct net *net)
{
#ifdef CONFIG_PROC_FSremove_proc_entry("ip_mr_cache", net->proc_net);remove_proc_entry("ip_mr_vif", net->proc_net);
#endifipmr_notifier_exit(net);ipmr_rules_exit(net);
}static struct pernet_operations ipmr_net_ops = {.init = ipmr_net_init,.exit = ipmr_net_exit,
};int __init ip_mr_init(void)
{int err;mrt_cachep = kmem_cache_create("ip_mrt_cache",sizeof(struct mfc_cache),0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,NULL);err = register_pernet_subsys(&ipmr_net_ops);if (err)goto reg_pernet_fail;err = register_netdevice_notifier(&ip_mr_notifier);if (err)goto reg_notif_fail;
#ifdef CONFIG_IP_PIMSM_V2if (inet_add_protocol(&pim_protocol, IPPROTO_PIM) < 0) {pr_err("%s: can't add PIM protocol\n", __func__);err = -EAGAIN;goto add_proto_fail;}
#endifrtnl_register(RTNL_FAMILY_IPMR, RTM_GETROUTE,ipmr_rtm_getroute, ipmr_rtm_dumproute, 0);rtnl_register(RTNL_FAMILY_IPMR, RTM_NEWROUTE,ipmr_rtm_route, NULL, 0);rtnl_register(RTNL_FAMILY_IPMR, RTM_DELROUTE,ipmr_rtm_route, NULL, 0);rtnl_register(RTNL_FAMILY_IPMR, RTM_GETLINK,NULL, ipmr_rtm_dumplink, 0);return 0;#ifdef CONFIG_IP_PIMSM_V2
add_proto_fail:unregister_netdevice_notifier(&ip_mr_notifier);
#endif
reg_notif_fail:unregister_pernet_subsys(&ipmr_net_ops);
reg_pernet_fail:kmem_cache_destroy(mrt_cachep);return err;
}net/ipv4/ipmr.c 是 Linux 内核中实现 IPv4 多播路由的核心文件，主要支持 mrouted 和 PIM（Protocol Independent Multicast）协议。以下是对其关键部分的详细分析：
1. 核心数据结构
a) 多播路由表 (struct mr_table)
管理多播路由信息，包含：
虚拟接口表 (
vif_table): 存储所有虚拟接口（VIF）信息。多播转发缓存 (MFC): 使用哈希表 (
mfc_hash) 存储已解析的路由条目。未解析队列 (
mfc_unres_queue): 临时存放待处理的多播包。定时器 (
ipmr_expire_timer): 清理超时未解析的条目。
b) 虚拟接口 (struct vif_device)
表示一个多播虚拟接口：
设备指针 (
dev): 关联的网络设备。本地/远程地址 (
local,remote): 隧道端点地址。统计信息: 收发包数、字节数等。
标志位 (
flags):VIFF_TUNNEL（隧道接口）、VIFF_REGISTER（注册到用户态）、VIFF_STATIC（静态配置）。
c) 多播转发缓存 (struct mfc_cache)
存储多播路由条目：
源地址/组地址 (
mfc_origin,mfc_mcastgrp): 标识流。输入接口 (
mfc_parent): 接收流量的 VIF。输出接口 TTL 映射 (
res.ttls): 每个 VIF 的 TTL 阈值。统计信息: 转发包数、字节数、错误计数。
2. 核心功能实现
a) 虚拟接口管理
创建 (
vif_add)
支持三种类型接口：VIFF_REGISTER: 注册到用户态守护进程（如pimd）。VIFF_TUNNEL: 创建 IP-in-IP 隧道（如 DVMRP）。物理接口: 绑定到实际网络设备。
删除 (
vif_delete)
解除设备绑定，更新统计，清理关联资源。
b) MFC 条目管理
动态学习 (
ipmr_cache_find)
通过哈希表快速查找 MFC 条目。静态配置 (
ipmr_mfc_add)
通过 Netlink 或 Socket 添加静态路由。超时处理 (
ipmr_expire_process)
清理未解析的 MFC 条目（默认 10 秒超时）。
c) 数据包转发 (ip_mr_forward)
处理流程：
查找 MFC: 匹配源地址和组地址。
验证输入接口: 检查包是否从正确 VIF 进入。
TTL 检查: 跳过 TTL 不足的出口。
克隆包多播转发:
隧道接口：封装 IP-in-IP 头。
物理接口：直接发送。
注册接口：提交给用户态守护进程。
d) 未解析包处理 (ipmr_cache_unresolved)
当 MFC 不存在时：
创建临时 MFC 条目并加入未解析队列。
发送
IGMPMSG_NOCACHE通知用户态。收到响应后解析条目并转发缓存的包。
3. 关键协议支持
a) PIM 协议处理
PIMv1 (
pim_rcv_v1)
处理 PIM 注册消息，封装包转发到 RP。PIMv2 (
pim_rcv)
校验消息有效性，转发到注册接口。
b) IGMP 消息
缓存报告 (
ipmr_cache_report)
发送IGMPMSG_WHOLEPKT通知用户态新流量。
4. 控制平面接口
a) Netlink 操作
路由操作 (
ipmr_rtm_route)
处理RTM_NEWROUTE/RTM_DELROUTE添加/删除 MFC。信息查询 (
ipmr_rtm_dumplink)
通过RTM_GETLINK返回 VIF 和 MFC 表信息。
b) Sysctl / Procfs
/proc/net/ip_mr_vif
显示所有 VIF 的统计信息。/proc/net/ip_mr_cache
列出 MFC 条目，包括源组地址、转发计数。
c) Socket IOCTL
SIOCGETVIFCNT
获取指定 VIF 的流量统计。SIOCGETSGCNT
查询特定多播流的转发统计。
5. 初始化和清理
初始化 (
ip_mr_init)注册网络子系统 (
register_pernet_subsys)。创建 MFC 缓存内存池 (
kmem_cache_create)。注册 Netlink 操作和 PIM 协议处理器。
挂载 Procfs 文件。
退出清理
释放所有路由表、定时器、Procfs 项。
6. 设计亮点
多表支持 (
CONFIG_IP_MROUTE_MULTIPLE_TABLES)
允许创建多个独立的多播路由表。高效查找
使用 RCU 保护的哈希表管理 MFC。用户态协作
通过原始套接字 (mroute_sk) 与mrouted/pimd交互。模块化结构
分离转发/控制逻辑，支持动态扩展。
总结
ipmr.c 实现了完整的 IPv4 多播路由框架，核心功能包括：
虚拟接口管理：支持物理接口、隧道和注册接口。
转发引擎：基于 MFC 条目高效克隆转发包。
协议支持：与 PIM/DVMRP 守护进程协同工作。
控制接口：提供 Netlink、IOCTL、Procfs 等管理方式。
其设计平衡了性能和灵活性，是 Linux 多播路由的基石。
