Merge branch 'x86/rdrand' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
[wandboard.git] / net / ipv4 / ip_forward.c
blob29a07b6c7168f7369b13e25d8c96011c6118ec56
1 /*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * The IP forwarding functionality.
8 * Authors: see ip.c
10 * Fixes:
11 * Many : Split from ip.c , see ip_input.c for
12 * history.
13 * Dave Gregorich : NULL ip_rt_put fix for multicast
14 * routing.
15 * Jos Vos : Add call_out_firewall before sending,
16 * use output device for accounting.
17 * Jos Vos : Call forward firewall after routing
18 * (always use output device).
19 * Mike McLagan : Routing by source
22 #include <linux/types.h>
23 #include <linux/mm.h>
24 #include <linux/skbuff.h>
25 #include <linux/ip.h>
26 #include <linux/icmp.h>
27 #include <linux/netdevice.h>
28 #include <linux/slab.h>
29 #include <net/sock.h>
30 #include <net/ip.h>
31 #include <net/tcp.h>
32 #include <net/udp.h>
33 #include <net/icmp.h>
34 #include <linux/tcp.h>
35 #include <linux/udp.h>
36 #include <linux/netfilter_ipv4.h>
37 #include <net/checksum.h>
38 #include <linux/route.h>
39 #include <net/route.h>
40 #include <net/xfrm.h>
42 static int ip_forward_finish(struct sk_buff *skb)
44 struct ip_options * opt = &(IPCB(skb)->opt);
46 IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
48 if (unlikely(opt->optlen))
49 ip_forward_options(skb);
51 return dst_output(skb);
54 int ip_forward(struct sk_buff *skb)
56 struct iphdr *iph; /* Our header */
57 struct rtable *rt; /* Route we use */
58 struct ip_options * opt = &(IPCB(skb)->opt);
60 if (skb_warn_if_lro(skb))
61 goto drop;
63 if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
64 goto drop;
66 if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
67 return NET_RX_SUCCESS;
69 if (skb->pkt_type != PACKET_HOST)
70 goto drop;
72 skb_forward_csum(skb);
75 * According to the RFC, we must first decrease the TTL field. If
76 * that reaches zero, we must reply an ICMP control message telling
77 * that the packet's lifetime expired.
79 if (ip_hdr(skb)->ttl <= 1)
80 goto too_many_hops;
82 if (!xfrm4_route_forward(skb))
83 goto drop;
85 rt = skb_rtable(skb);
87 if (opt->is_strictroute && opt->nexthop != rt->rt_gateway)
88 goto sr_failed;
90 if (unlikely(skb->len > dst_mtu(&rt->dst) && !skb_is_gso(skb) &&
91 (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
92 IP_INC_STATS(dev_net(rt->dst.dev), IPSTATS_MIB_FRAGFAILS);
93 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
94 htonl(dst_mtu(&rt->dst)));
95 goto drop;
98 /* We are about to mangle packet. Copy it! */
99 if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->dst.header_len))
100 goto drop;
101 iph = ip_hdr(skb);
103 /* Decrease ttl after skb cow done */
104 ip_decrease_ttl(iph);
107 * We now generate an ICMP HOST REDIRECT giving the route
108 * we calculated.
110 if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb_sec_path(skb))
111 ip_rt_send_redirect(skb);
113 skb->priority = rt_tos2priority(iph->tos);
115 return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, skb, skb->dev,
116 rt->dst.dev, ip_forward_finish);
118 sr_failed:
120 * Strict routing permits no gatewaying
122 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
123 goto drop;
125 too_many_hops:
126 /* Tell the sender its packet died... */
127 IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_INHDRERRORS);
128 icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
129 drop:
130 kfree_skb(skb);
131 return NET_RX_DROP;