Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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kernel
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linux
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.
5 *
6 * The IP forwarding functionality.
7 *
8 * Authors: see ip.c
9 *
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
20 */
21
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 <net/sock.h>
29#include <net/ip.h>
30#include <net/tcp.h>
31#include <net/udp.h>
32#include <net/icmp.h>
33#include <linux/tcp.h>
34#include <linux/udp.h>
35#include <linux/netfilter_ipv4.h>
36#include <net/checksum.h>
37#include <linux/route.h>
38#include <net/route.h>
39#include <net/xfrm.h>
40
41static int ip_forward_finish(struct sk_buff *skb)
42{
43 struct ip_options * opt = &(IPCB(skb)->opt);
44
45 IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
46
47 if (unlikely(opt->optlen))
48 ip_forward_options(skb);
49
50 return dst_output(skb);
51}
52
53int ip_forward(struct sk_buff *skb)
54{
55 struct iphdr *iph; /* Our header */
56 struct rtable *rt; /* Route we use */
57 struct ip_options * opt = &(IPCB(skb)->opt);
58
59 if (skb_warn_if_lro(skb))
60 goto drop;
61
62 if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
63 goto drop;
64
65 if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
66 return NET_RX_SUCCESS;
67
68 if (skb->pkt_type != PACKET_HOST)
69 goto drop;
70
71 skb_forward_csum(skb);
72
73 /*
74 * According to the RFC, we must first decrease the TTL field. If
75 * that reaches zero, we must reply an ICMP control message telling
76 * that the packet's lifetime expired.
77 */
78 if (ip_hdr(skb)->ttl <= 1)
79 goto too_many_hops;
80
81 if (!xfrm4_route_forward(skb))
82 goto drop;
83
84 rt = skb_rtable(skb);
85
86 if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
87 goto sr_failed;
88
89 if (unlikely(skb->len > dst_mtu(&rt->u.dst) && !skb_is_gso(skb) &&
90 (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
91 IP_INC_STATS(dev_net(rt->u.dst.dev), IPSTATS_MIB_FRAGFAILS);
92 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
93 htonl(dst_mtu(&rt->u.dst)));
94 goto drop;
95 }
96
97 /* We are about to mangle packet. Copy it! */
98 if (skb_cow(skb, LL_RESERVED_SPACE(rt->u.dst.dev)+rt->u.dst.header_len))
99 goto drop;
100 iph = ip_hdr(skb);
101
102 /* Decrease ttl after skb cow done */
103 ip_decrease_ttl(iph);
104
105 /*
106 * We now generate an ICMP HOST REDIRECT giving the route
107 * we calculated.
108 */
109 if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb_sec_path(skb))
110 ip_rt_send_redirect(skb);
111
112 skb->priority = rt_tos2priority(iph->tos);
113
114 return NF_HOOK(PF_INET, NF_INET_FORWARD, skb, skb->dev, rt->u.dst.dev,
115 ip_forward_finish);
116
117sr_failed:
118 /*
119 * Strict routing permits no gatewaying
120 */
121 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
122 goto drop;
123
124too_many_hops:
125 /* Tell the sender its packet died... */
126 IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_INHDRERRORS);
127 icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
128drop:
129 kfree_skb(skb);
130 return NET_RX_DROP;
131}