基于linux-2.6.31的IPV6的数据包接收流程分析
接收的流程为:ipv6_rcv--->ipv6_rcv_finish---->dst_input-àip6_input-àip6_input_finish
或者ipv6_rcv--->ipv6_rcv_finish---->ip6_route_input或者ipv6_rcv--->ipv6_rcv_finish---->dst_input-àip6_forward-àip6_forward_finish
static struct packet_type ipv6_packet_type__read_mostly = {
.type= cpu_to_be16(ETH_P_IPV6),
.func= ipv6_rcv,
.gso_send_check= ipv6_gso_send_check,
.gso_segment= ipv6_gso_segment,
.gro_receive= ipv6_gro_receive,
.gro_complete= ipv6_gro_complete,
};
//执行一些检查,判断数据包是否转发、有效性、正确性
intipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,struct net_device *orig_dev)
{
structipv6hdr *hdr;
u32 pkt_len;
structinet6_dev *idev;
//获取数据包网卡
structnet *net = dev_net(skb->dev);
//丢弃发送给其他主机的数据包
if(skb->pkt_type == PACKET_OTHERHOST) {
kfree_skb(skb);
return0;
}
rcu_read_lock();
idev= __in6_dev_get(skb->dev);
IP6_UPD_PO_STATS_BH(net,idev, IPSTATS_MIB_IN, skb->len);
//
if((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL ||
!idev ||unlikely(idev->cnf.disable_ipv6)) {
IP6_INC_STATS_BH(net,idev, IPSTATS_MIB_INDISCARDS);
gotodrop;
}
memset(IP6CB(skb),0, sizeof(struct inet6_skb_parm));
/*
* Store incoming device index. When the packetwill
* be queued, we cannot refer to skb->devanymore.
*
* BTW, when we send a packet for our own localaddress on a
* non-loopback interface (e.g. ethX), it isbeing delivered
* via the loopback interface (lo) here;skb->dev = loopback_dev.
* It, however, should be considered as if itis being
* arrived via the sending interface (ethX),because of the
* nature of scoping architecture. --yoshfuji
*/
//保存入口设备索引
IP6CB(skb)->iif= skb_dst(skb) ? ip6_dst_idev(skb_dst(skb))->dev->ifindex : dev->ifindex;
//检查数据包长度是否为IP报头的长度
if(unlikely(!pskb_may_pull(skb, sizeof(*hdr))))
gotoerr;
//获取IPv6报头位置
hdr= ipv6_hdr(skb);
//检查版本是否为IPv6
if(hdr->version != 6)
gotoerr;
/*
* RFC4291 2.5.3
* A packet received on an interface with adestination address
* of loopback must be dropped.
*/
//丢弃环路数据包
if(!(dev->flags & IFF_LOOPBACK) &&
ipv6_addr_loopback(&hdr->daddr))
gotoerr;
skb->transport_header= skb->network_header + sizeof(*hdr);
IP6CB(skb)->nhoff= offsetof(struct ipv6hdr, nexthdr);
pkt_len= ntohs(hdr->payload_len);
//处理Jumbo负载选项
/*pkt_len may be zero if Jumbo payload option is present */
if(pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
if(pkt_len + sizeof(struct ipv6hdr) > skb->len) {
IP6_INC_STATS_BH(net,
idev, IPSTATS_MIB_INTRUNCATEDPKTS);
gotodrop;
}
if(pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr))) {
IP6_INC_STATS_BH(net,idev, IPSTATS_MIB_INHDRERRORS);
gotodrop;
}
hdr= ipv6_hdr(skb);
}
if(hdr->nexthdr == NEXTHDR_HOP) {
if(ipv6_parse_hopopts(skb) < 0) {
IP6_INC_STATS_BH(net,idev, IPSTATS_MIB_INHDRERRORS);
rcu_read_unlock();
return0;
}
}
rcu_read_unlock();
/*Must drop socket now because of tproxy. */
skb_orphan(skb);
//由过滤器调用IP6_rcv_finish函数进一步处理数据包
returnNF_HOOK(PF_INET6, NF_INET_PRE_ROUTING, skb, dev, NULL,
ip6_rcv_finish);
err:
IP6_INC_STATS_BH(net,idev, IPSTATS_MIB_INHDRERRORS);
drop:
rcu_read_unlock();
kfree_skb(skb);
return0;
}
//如果路由表项信息已经缓存在套接字缓冲区的dst字段,则直接用skb->dst->input指向的函数;否则,调用ip6_rout_input函数查找路由表,返回skb->dst->input的具体内容
inlineint ip6_rcv_finish( struct sk_buff *skb)
{
if(skb_dst(skb) == NULL)
ip6_route_input(skb);
returndst_input(skb);
}
//获取目的地址描述符
static inlinestruct dst_entry *skb_dst(const struct sk_buff *skb)
{
return (struct dst_entry*)skb->_skb_dst;
}
/* Input packetfrom network to transport.
将数据包从网络层送到传输层
*/
static inline int dst_input(struct sk_buff *skb)
{
return skb_dst(skb)->input(skb);
}
//交给路由模块
void ip6_route_input(struct sk_buff *skb)
{
struct ipv6hdr *iph = ipv6_hdr(skb);
struct net *net = dev_net(skb->dev);
int flags = RT6_LOOKUP_F_HAS_SADDR;
struct flowi fl = {
.iif = skb->dev->ifindex,
.nl_u = {
.ip6_u = {
.daddr =iph->daddr,
.saddr =iph->saddr,
.flowlabel= (* (__be32 *) iph)&IPV6_FLOWINFO_MASK,
},
},
.mark = skb->mark,
.proto = iph->nexthdr,
};
if (rt6_need_strict(&iph->daddr)&& skb->dev->type != ARPHRD_PIMREG)
flags |= RT6_LOOKUP_F_IFACE;
skb_dst_set(skb, fib6_rule_lookup(net,&fl, flags, ip6_pol_route_input));
}
intip6_input(struct sk_buff *skb)
{
returnNF_HOOK(PF_INET6, NF_INET_LOCAL_IN, skb, skb->dev, NULL,
ip6_input_finish);
}
staticint ip6_input_finish(struct sk_buff *skb)
{
structinet6_protocol *ipprot;
unsignedint nhoff;
intnexthdr, raw;
u8hash;
structinet6_dev *idev;
structnet *net = dev_net(skb_dst(skb)->dev);
/*
* Parseextension headers解析扩展头
*/
rcu_read_lock();
resubmit:
//指向目的设备
idev= ip6_dst_idev(skb_dst(skb));
//检查数据包长度是否是传输层头部
if(!pskb_pull(skb, skb_transport_offset(skb)))
gotodiscard;
// #define IP6CB(skb) ((struct inet6_skb_parm*)((skb)->cb))
nhoff= IP6CB(skb)->nhoff;
//获取下一个扩展头部
nexthdr= skb_network_header(skb)[nhoff];
/*
int raw6_local_deliver(struct sk_buff *skb,int nexthdr)
{
structsock *raw_sk;
//判断可否通过原始套接字接受数据,如果可以,则返回对应原始套接字,并通过ipv6_raw_deliver函数接受套接字缓冲区中的数据内容
raw_sk= sk_head(&raw_v6_hashinfo.ht[nexthdr & (MAX_INET_PROTOS - 1)]);
if(raw_sk && !ipv6_raw_deliver(skb, nexthdr))
raw_sk= NULL;
returnraw_sk != NULL;
}
*/
raw= raw6_local_deliver(skb, nexthdr);
//查找inet6_protos表,确定是否注册过第四层协议,如果有,则调用对应的函数来接受数据包
hash= nexthdr & (MAX_INET_PROTOS - 1);
if((ipprot = rcu_dereference(inet6_protos[hash])) != NULL) {
intret;
if(ipprot->flags & INET6_PROTO_FINAL) {
structipv6hdr *hdr;
/*Free reference early: we don't need it any more,
and it may hold ip_conntrack module loaded
indefinitely. */
nf_reset(skb);
skb_postpull_rcsum(skb,skb_network_header(skb),
skb_network_header_len(skb));
hdr= ipv6_hdr(skb);
if(ipv6_addr_is_multicast(&hdr->daddr) &&
!ipv6_chk_mcast_addr(skb->dev,&hdr->daddr,
&hdr->saddr) &&
!ipv6_is_mld(skb, nexthdr))
gotodiscard;
}
if(!(ipprot->flags & INET6_PROTO_NOPOLICY) &&
!xfrm6_policy_check(NULL, XFRM_POLICY_IN,skb))
gotodiscard;
//通过ipprot的handler指针调用上层协议的接受函数;
//对于TCP,调用tcp_v6_rcv;对于UDP,调用udpv6_rcv;对于ICMP,调用icmpv6_rcv
ret= ipprot->handler(skb);
if(ret > 0)
goto resubmit;
elseif (ret == 0)
IP6_INC_STATS_BH(net,idev, IPSTATS_MIB_INDELIVERS);
}else {
if(!raw) {
if(xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
IP6_INC_STATS_BH(net,idev,
IPSTATS_MIB_INUNKNOWNPROTOS);
icmpv6_send(skb,ICMPV6_PARAMPROB,
ICMPV6_UNK_NEXTHDR, nhoff,
skb->dev);
}
}else
IP6_INC_STATS_BH(net,idev, IPSTATS_MIB_INDELIVERS);
kfree_skb(skb);
}
rcu_read_unlock();
return0;
discard:
IP6_INC_STATS_BH(net,idev, IPSTATS_MIB_INDISCARDS);
rcu_read_unlock();
kfree_skb(skb);
return0;
}
更多推荐
所有评论(0)