Release 4.15 net/ipv4/ip_forward.c

// SPDX-License-Identifier: GPL-2.0
/*
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              The IP forwarding functionality.
 *
 * Authors:     see ip.c
 *
 * Fixes:
 *              Many            :       Split from ip.c , see ip_input.c for
 *                                      history.
 *              Dave Gregorich  :       NULL ip_rt_put fix for multicast
 *                                      routing.
 *              Jos Vos         :       Add call_out_firewall before sending,
 *                                      use output device for accounting.
 *              Jos Vos         :       Call forward firewall after routing
 *                                      (always use output device).
 *              Mike McLagan    :       Routing by source
 */

#include <linux/types.h>
#include <linux/mm.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/netdevice.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/netfilter_ipv4.h>
#include <net/checksum.h>
#include <linux/route.h>
#include <net/route.h>
#include <net/xfrm.h>



static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
{
	if (skb->len <= mtu)
		return false;

	if (unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0))
		return false;

	/* original fragment exceeds mtu and DF is set */
	if (unlikely(IPCB(skb)->frag_max_size > mtu))
		return true;

	if (skb->ignore_df)
		return false;

	if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))
		return false;

	return true;
}


Contributors
Person
Tokens
Prop
Commits
CommitProp
Florian Westphal
95
96.94%
2
66.67%
Marcelo Ricardo Leitner
3
3.06%
1
33.33%
Total
98
100.00%
3
100.00%



static int ip_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);
}

Contributors
Person
Tokens
Prop
Commits
CommitProp
Linus Torvalds (pre-git)
45
57.69%
5
31.25%
Eric W. Biedermann
10
12.82%
4
25.00%
Vincent Bernat
9
11.54%
1
6.25%
David S. Miller
7
8.97%
1
6.25%
Alexey Kuznetsov
3
3.85%
1
6.25%
Eric Dumazet
2
2.56%
2
12.50%
Hideaki Yoshifuji / 吉藤英明
1
1.28%
1
6.25%
Pavel Emelyanov
1
1.28%
1
6.25%
Total
78
100.00%
16
100.00%



int ip_forward(struct sk_buff *skb)
{
	u32 mtu;
	struct iphdr *iph;	/* Our header */
	struct rtable *rt;	/* Route we use */
	struct ip_options *opt	= &(IPCB(skb)->opt);
	struct net *net;

	/* that should never happen */
	if (skb->pkt_type != PACKET_HOST)
		goto drop;

	if (unlikely(skb->sk))
		goto drop;

	if (skb_warn_if_lro(skb))
		goto drop;

	if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
		goto drop;

	if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
		return NET_RX_SUCCESS;

	skb_forward_csum(skb);
	net = dev_net(skb->dev);

	/*
         *      According to the RFC, we must first decrease the TTL field. If
         *      that reaches zero, we must reply an ICMP control message telling
         *      that the packet's lifetime expired.
         */
	if (ip_hdr(skb)->ttl <= 1)
		goto too_many_hops;

	if (!xfrm4_route_forward(skb))
		goto drop;

	rt = skb_rtable(skb);

	if (opt->is_strictroute && rt->rt_uses_gateway)
		goto sr_failed;

	IPCB(skb)->flags |= IPSKB_FORWARDED;
	mtu = ip_dst_mtu_maybe_forward(&rt->dst, true);
	if (ip_exceeds_mtu(skb, mtu)) {
		IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
			  htonl(mtu));
		goto drop;
	}

	/* We are about to mangle packet. Copy it! */
	if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->dst.header_len))
		goto drop;
	iph = ip_hdr(skb);

	/* Decrease ttl after skb cow done */
	ip_decrease_ttl(iph);

	/*
         *      We now generate an ICMP HOST REDIRECT giving the route
         *      we calculated.
         */
	if (IPCB(skb)->flags & IPSKB_DOREDIRECT && !opt->srr &&
	    !skb_sec_path(skb))
		ip_rt_send_redirect(skb);

	skb->priority = rt_tos2priority(iph->tos);

	return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD,
		       net, NULL, skb, skb->dev, rt->dst.dev,
		       ip_forward_finish);

sr_failed:
	/*
         *      Strict routing permits no gatewaying
         */
	 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
	 goto drop;

too_many_hops:
	/* Tell the sender its packet died... */
	__IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS);
	icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
drop:
	kfree_skb(skb);
	return NET_RX_DROP;
}
Contributors
Person
Tokens
Prop
Commits
CommitProp
Linus Torvalds (pre-git)
167
43.83%
11
27.50%
Alexey Kuznetsov
60
15.75%
4
10.00%
John Heffner
36
9.45%
1
2.50%
Hannes Frederic Sowa
24
6.30%
2
5.00%
Eric W. Biedermann
18
4.72%
2
5.00%
Denis Kirjanov
12
3.15%
1
2.50%
Sebastian Pöhn
12
3.15%
1
2.50%
Ben Hutchings
10
2.62%
1
2.50%
Arnaldo Carvalho de Melo
6
1.57%
1
2.50%
Linus Torvalds
5
1.31%
1
2.50%
Eric Dumazet
4
1.05%
2
5.00%
Wei Dong
4
1.05%
1
2.50%
Alexey Dobriyan
3
0.79%
1
2.50%
Masahide Nakamura
3
0.79%
1
2.50%
Herbert Xu
3
0.79%
1
2.50%
Florian Westphal
3
0.79%
1
2.50%
Pavel Emelyanov
2
0.52%
2
5.00%
Thomas Graf
2
0.52%
1
2.50%
Hideaki Yoshifuji / 吉藤英明
2
0.52%
1
2.50%
David S. Miller
2
0.52%
1
2.50%
Jan Engelhardt
1
0.26%
1
2.50%
Julian Anastasov
1
0.26%
1
2.50%
Patrick McHardy
1
0.26%
1
2.50%
Total
381
100.00%
40
100.00%

Overall Contributors
Person
Tokens
Prop
Commits
CommitProp
Linus Torvalds (pre-git)
263
42.69%
14
25.00%
Florian Westphal
98
15.91%
2
3.57%
Alexey Kuznetsov
66
10.71%
5
8.93%
John Heffner
36
5.84%
1
1.79%
Eric W. Biedermann
28
4.55%
6
10.71%
Hannes Frederic Sowa
24
3.90%
2
3.57%
Denis Kirjanov
12
1.95%
1
1.79%
Sebastian Pöhn
12
1.95%
1
1.79%
Ben Hutchings
10
1.62%
1
1.79%
David S. Miller
9
1.46%
1
1.79%
Vincent Bernat
9
1.46%
1
1.79%
Arnaldo Carvalho de Melo
6
0.97%
1
1.79%
Eric Dumazet
6
0.97%
3
5.36%
Linus Torvalds
5
0.81%
1
1.79%
Wei Dong
4
0.65%
1
1.79%
Tejun Heo
3
0.49%
1
1.79%
Marcelo Ricardo Leitner
3
0.49%
1
1.79%
Masahide Nakamura
3
0.49%
1
1.79%
Alexey Dobriyan
3
0.49%
1
1.79%
Pavel Emelyanov
3
0.49%
2
3.57%
Hideaki Yoshifuji / 吉藤英明
3
0.49%
2
3.57%
Herbert Xu
3
0.49%
1
1.79%
Thomas Graf
2
0.32%
1
1.79%
Adrian Bunk
1
0.16%
1
1.79%
Jan Engelhardt
1
0.16%
1
1.79%
Julian Anastasov
1
0.16%
1
1.79%
Patrick McHardy
1
0.16%
1
1.79%
Greg Kroah-Hartman
1
0.16%
1
1.79%
Total
616
100.00%
56
100.00%
Directory: net/ipv4

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