ip_rcv_finish

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<h3 class="title pre fs1"><span class="tcnt">ip_rcv_finish</span>  <span class="bgc0 fc07 fw0 fs0"></span></h3>
<p class="tdep clearfix nbw-act fc06" style="line-height:20px"><span class="pleft"><span class="blogsep">2013-04-20 14:37:14</span><span class="blogsep">|  分类：</span> <a class="fc03 m2a" href="http://h1372865100.blog.163.com/blog/#m=0&t=1&c=fks_084069086084083074087086080095086087081071086095087067087" rel="noopener noreferrer" target="_blank" title="linux-NET"> linux-NET</a> </span><span class="pright fc07 ztag"><span class="blogsep">|</span><span class="fc03 m2a" id="$_spanReport">举报</span></span> <span class="pright fc07 ztag"><span class="blogsep">|</span><span class="zihao fc03" id="$_fontswitch">字号</span></span><span class="pright pnt fc03" id="$_blog_subscribe"><span class="iblock icn0 icn0-919"> </span><a class="m2a" target="_blank">订阅</a></span> </p>
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执行完钩子函数后，IP数据包被传送到ip_rcv_finish做进一步处理，这个函数主要功能是做路由选择（kernel/net/ipv4/ip_input.c）
<br> static int ip_rcv_finish(struct sk_buff *skb)
<br> {
<br>    const struct iphdr *iph = ip_hdr(skb);
<br>    struct rtable *rt;
<br>
<br>    /*
<br>    * Initialise the virtual path cache for the packet. It describes
<br>    * how the packet travels inside Linux networking.
<br>    */
<br>    if (skb_dst(skb) == NULL) {
<br>       int err =
<span style="color:#ff0000">ip_route_input_noref</span>(skb, iph->daddr, iph->saddr,
<br>                         iph->tos, skb->dev);
<br>       if (unlikely(err)) {
<br>          if (err == -EHOSTUNREACH)
<br>                IP_INC_STATS_BH(dev_net(skb->dev),
<br>                      IPSTATS_MIB_INADDRERRORS);
<br>          else if (err == -ENETUNREACH)
<br>                IP_INC_STATS_BH(dev_net(skb->dev),
<br>                      IPSTATS_MIB_INNOROUTES);
<br>          else if (err == -EXDEV)
<br>                NET_INC_STATS_BH(dev_net(skb->dev),
<br>                         LINUX_MIB_IPRPFILTER);
<br>          goto drop;
<br>       }
<br>    }
<br>
<br> #ifdef CONFIG_IP_ROUTE_CLASSID
<br>    if (unlikely(skb_dst(skb)->tclassid)) {
<br>       struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct);
<br>       u32 idx = skb_dst(skb)->tclassid;
<br>       st[idx&0xFF].o_packets++;
<br>       st[idx&0xFF].o_bytes += skb->len;
<br>       st[(idx>>16)&0xFF].i_packets++;
<br>       st[(idx>>16)&0xFF].i_bytes += skb->len;
<br>    }
<br> #endif
<br>
<br>    if (iph->ihl > 5 && ip_rcv_options(skb))
<br>       goto drop;
<br>
<br>    rt = skb_rtable(skb);
<br>    if (rt->rt_type == RTN_MULTICAST) {
<br>       IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INMCAST,
<br>                skb->len);
<br>    } else if (rt->rt_type == RTN_BROADCAST)
<br>       IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST,
<br>                skb->len);
<br>
<br>    return dst_input(skb);
<br>
<br> drop:
<br>    kfree_skb(skb);
<br>    return NET_RX_DROP;
<br> }
<br> 我们现看(kernel/include/net/route.h)ip_route_input_noref()--->(kernel/net/route.c)ip_route_input_common()
<br>
<br>
<br> int ip_route_input_common(struct sk_buff *skb, __be32 daddr, __be32 saddr,
<br>             u8 tos, struct net_device *dev, bool noref)
<br> {
<br>    struct rtable * rth;
<br>    unsigned hash;
<br>    int iif = dev->ifindex;
<br>    struct net *net;
<br>    int res;
<br>
<br>    net = dev_net(dev);
<br>
<br>    rcu_read_lock();
<br>
<br>    if (!rt_caching(net))
<br>       goto skip_cache;
<br>
<br>    tos &= IPTOS_RT_MASK;
<br>    hash = rt_hash(daddr, sadd