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ip: generate unique IP identificator if local fragmentation is allowed

Browse source 
If local fragmentation is allowed, then ip_select_ident() and
ip_select_ident_more() need to generate unique IDs to ensure
correct defragmentation on the peer.

For example, if IPsec (tunnel mode) has to encrypt large skbs
that have local_df bit set, then all IP fragments that belonged
to different ESP datagrams would have used the same identificator.
If one of these IP fragments would get lost or reordered, then
peer could possibly stitch together wrong IP fragments that did
not belong to the same datagram. This would lead to a packet loss
or data corruption.

Signed-off-by: Ansis Atteka <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Ansis Atteka 2013-09-18 15:29:53 -07:00 • committed by David S. Miller
commit 703133de33
9 changed files with 20 additions and 16 deletions
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4
net/ipv4/igmp.c
View file

@ -369,7 +369,7 @@ static struct sk_buff *igmpv3_newpack(struct net_device *dev, int size)
pip->saddr = fl4.saddr;
pip->protocol = IPPROTO_IGMP;
pip->tot_len = 0; /* filled in later */
ip_select_ident(pip, &rt->dst, NULL);
ip_select_ident(skb, &rt->dst, NULL);
((u8 *)&pip[1])[0] = IPOPT_RA;
((u8 *)&pip[1])[1] = 4;
((u8 *)&pip[1])[2] = 0;
@ -714,7 +714,7 @@ static int igmp_send_report(struct in_device *in_dev, struct ip_mc_list *pmc,
iph->daddr = dst;
iph->saddr = fl4.saddr;
iph->protocol = IPPROTO_IGMP;
ip_select_ident(iph, &rt->dst, NULL);
ip_select_ident(skb, &rt->dst, NULL);
((u8 *)&iph[1])[0] = IPOPT_RA;
((u8 *)&iph[1])[1] = 4;
((u8 *)&iph[1])[2] = 0;

4
net/ipv4/inetpeer.c
View file

@ -32,8 +32,8 @@
* At the moment of writing this notes identifier of IP packets is generated
* to be unpredictable using this code only for packets subjected
* (actually or potentially) to defragmentation. I.e. DF packets less than
* PMTU in size uses a constant ID and do not use this code (see
* ip_select_ident() in include/net/ip.h).
* PMTU in size when local fragmentation is disabled use a constant ID and do
* not use this code (see ip_select_ident() in include/net/ip.h).
*
* Route cache entries hold references to our nodes.
* New cache entries get references via lookup by destination IP address in

6
net/ipv4/ip_output.c
View file

@ -148,7 +148,7 @@ int ip_build_and_send_pkt(struct sk_buff *skb, struct sock *sk,
iph->daddr = (opt && opt->opt.srr ? opt->opt.faddr : daddr);
iph->saddr = saddr;
iph->protocol = sk->sk_protocol;
ip_select_ident(iph, &rt->dst, sk);
ip_select_ident(skb, &rt->dst, sk);
if (opt && opt->opt.optlen) {
iph->ihl += opt->opt.optlen>>2;
@ -386,7 +386,7 @@ packet_routed:
ip_options_build(skb, &inet_opt->opt, inet->inet_daddr, rt, 0);
}
ip_select_ident_more(iph, &rt->dst, sk,
ip_select_ident_more(skb, &rt->dst, sk,
(skb_shinfo(skb)->gso_segs ?: 1) - 1);
skb->priority = sk->sk_priority;
@ -1324,7 +1324,7 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
iph->ttl = ttl;
iph->protocol = sk->sk_protocol;
ip_copy_addrs(iph, fl4);
ip_select_ident(iph, &rt->dst, sk);
ip_select_ident(skb, &rt->dst, sk);
if (opt) {
iph->ihl += opt->optlen>>2;

2
net/ipv4/ipmr.c
View file

@ -1658,7 +1658,7 @@ static void ip_encap(struct sk_buff *skb, __be32 saddr, __be32 daddr)
iph->protocol = IPPROTO_IPIP;
iph->ihl = 5;
iph->tot_len = htons(skb->len);
ip_select_ident(iph, skb_dst(skb), NULL);
ip_select_ident(skb, skb_dst(skb), NULL);
ip_send_check(iph);
memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));

2
net/ipv4/raw.c
View file

@ -387,7 +387,7 @@ static int raw_send_hdrinc(struct sock *sk, struct flowi4 *fl4,
iph->check = 0;
iph->tot_len = htons(length);
if (!iph->id)
ip_select_ident(iph, &rt->dst, NULL);
ip_select_ident(skb, &rt->dst, NULL);
iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
}

2
net/ipv4/xfrm4_mode_tunnel.c
View file

@ -117,7 +117,7 @@ static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
top_iph->frag_off = (flags & XFRM_STATE_NOPMTUDISC) ?
0 : (XFRM_MODE_SKB_CB(skb)->frag_off & htons(IP_DF));
ip_select_ident(top_iph, dst->child, NULL);
ip_select_ident(skb, dst->child, NULL);
top_iph->ttl = ip4_dst_hoplimit(dst->child);