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ipvs: Decrement ttl

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We decrement the IP ttl in all the modes in order to prevent infinite
route loops. The changes were done based on Julian Anastasov's
suggestions in a prior thread.

The ttl based check/discard and the actual decrement are done in
__ip_vs_get_out_rt() and in __ip_vs_get_out_rt_v6(), for the IPv6
case. decrement_ttl() implements the actual functionality for the
two cases.

Signed-off-by: Dwip Banerjee <dwip@linux.vnet.ibm.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
This commit is contained in:
Dwip Banerjee 2016-10-26 12:14:42 -05:00 committed by Simon Horman
parent fe24a0c3a9
commit 8d8e20e2d7
1 changed files with 54 additions and 0 deletions
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54
net/netfilter/ipvs/ip_vs_xmit.c
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@ -254,6 +254,54 @@ static inline bool ensure_mtu_is_adequate(struct netns_ipvs *ipvs, int skb_af,
return true;
}
static inline bool decrement_ttl(struct netns_ipvs *ipvs,
int skb_af,
struct sk_buff *skb)
{
struct net *net = ipvs->net;
#ifdef CONFIG_IP_VS_IPV6
if (skb_af == AF_INET6) {
struct dst_entry *dst = skb_dst(skb);
/* check and decrement ttl */
if (ipv6_hdr(skb)->hop_limit <= 1) {
/* Force OUTPUT device used as source address */
skb->dev = dst->dev;
icmpv6_send(skb, ICMPV6_TIME_EXCEED,
ICMPV6_EXC_HOPLIMIT, 0);
__IP6_INC_STATS(net, ip6_dst_idev(dst),
IPSTATS_MIB_INHDRERRORS);
return false;
}
/* don't propagate ttl change to cloned packets */
if (!skb_make_writable(skb, sizeof(struct ipv6hdr)))
return false;
ipv6_hdr(skb)->hop_limit--;
} else
#endif
{
if (ip_hdr(skb)->ttl <= 1) {
/* Tell the sender its packet died... */
__IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS);
icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
return false;
}
/* don't propagate ttl change to cloned packets */
if (!skb_make_writable(skb, sizeof(struct iphdr)))
return false;
/* Decrease ttl */
ip_decrease_ttl(ip_hdr(skb));
}
return true;
}
/* Get route to destination or remote server */
static int
__ip_vs_get_out_rt(struct netns_ipvs *ipvs, int skb_af, struct sk_buff *skb,
@ -326,6 +374,9 @@ __ip_vs_get_out_rt(struct netns_ipvs *ipvs, int skb_af, struct sk_buff *skb,
return local;
}
if (!decrement_ttl(ipvs, skb_af, skb))
goto err_put;
if (likely(!(rt_mode & IP_VS_RT_MODE_TUNNEL))) {
mtu = dst_mtu(&rt->dst);
} else {
@ -473,6 +524,9 @@ __ip_vs_get_out_rt_v6(struct netns_ipvs *ipvs, int skb_af, struct sk_buff *skb,
return local;
}
if (!decrement_ttl(ipvs, skb_af, skb))
goto err_put;
/* MTU checking */
if (likely(!(rt_mode & IP_VS_RT_MODE_TUNNEL)))
mtu = dst_mtu(&rt->dst);