From 8d8e20e2d7bba8c50e64e0eca1cb83956f468e49 Mon Sep 17 00:00:00 2001 From: Dwip Banerjee Date: Wed, 26 Oct 2016 12:14:42 -0500 Subject: [PATCH] ipvs: Decrement ttl 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 Acked-by: Julian Anastasov Signed-off-by: Simon Horman --- net/netfilter/ipvs/ip_vs_xmit.c | 54 +++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c index 01d3d894de463..4e1a98fcc8c3f 100644 --- a/net/netfilter/ipvs/ip_vs_xmit.c +++ b/net/netfilter/ipvs/ip_vs_xmit.c @@ -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);