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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 <= 1) 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. Because of the ttl change, the skb_make_writable() guard is
also invoked therein.
The !ip_vs_iph_icmp(ipvsh) checks are removed from
ensure_mtu_is_adequate() as they seem unnecessary (icmp code doesn't
send ICMP error in response to another ICMP error).
Signed-off-by: Dwip Banerjee <dwip@xxxxxxxxxxxxxxxxxx>
---
diff --git a/net/netfilter/ipvs/ip_vs_xmit.c
b/net/netfilter/ipvs/ip_vs_xmit.c
index 01d3d89..e3586bd 100644
--- a/net/netfilter/ipvs/ip_vs_xmit.c
+++ b/net/netfilter/ipvs/ip_vs_xmit.c
@@ -225,7 +225,7 @@ static inline bool ensure_mtu_is_adequate(struct
netns_ipvs *ipvs, int skb_af,
if (!skb->dev)
skb->dev = net->loopback_dev;
/* only send ICMP too big on first fragment */
- if (!ipvsh->fragoffs && !ip_vs_iph_icmp(ipvsh))
+ if (!ipvsh->fragoffs)
icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
IP_VS_DBG(1, "frag needed for %pI6c\n",
&ipv6_hdr(skb)->saddr);
@@ -241,8 +241,7 @@ static inline bool ensure_mtu_is_adequate(struct
netns_ipvs *ipvs, int skb_af,
return true;
if (unlikely(ip_hdr(skb)->frag_off & htons(IP_DF) &&
- skb->len > mtu && !skb_is_gso(skb) &&
- !ip_vs_iph_icmp(ipvsh))) {
+ skb->len > mtu && !skb_is_gso(skb))) {
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
htonl(mtu));
IP_VS_DBG(1, "frag needed for %pI4\n",
@@ -266,6 +265,7 @@ __ip_vs_get_out_rt(struct netns_ipvs *ipvs, int
skb_af, struct sk_buff *skb,
struct rtable *rt; /* Route to the other host */
int mtu;
int local, noref = 1;
+ struct iphdr *iph = ip_hdr(skb);
if (dest) {
dest_dst = __ip_vs_dst_check(dest);
@@ -326,6 +326,14 @@ __ip_vs_get_out_rt(struct netns_ipvs *ipvs, int
skb_af, struct sk_buff *skb,
return local;
}
+ if (iph->ttl <= 1) {
+ /* Tell the sender its packet died... */
+ __IP_INC_STATS(dev_net(skb_dst(skb)->dev),
+ IPSTATS_MIB_INHDRERRORS);
+ icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
+ goto err_put;
+ }
+
if (likely(!(rt_mode & IP_VS_RT_MODE_TUNNEL))) {
mtu = dst_mtu(&rt->dst);
} else {
@@ -349,6 +357,13 @@ __ip_vs_get_out_rt(struct netns_ipvs *ipvs, int
skb_af, struct sk_buff *skb,
} else
skb_dst_set(skb, &rt->dst);
+ /* don't propagate ttl change to cloned packets */
+ if (!skb_make_writable(skb, sizeof(struct iphdr)))
+ goto err_put;
+
+ /* Decrease ttl */
+ ip_decrease_ttl(iph);
+
return local;
err_put:
@@ -414,6 +429,7 @@ __ip_vs_get_out_rt_v6(struct netns_ipvs *ipvs, int
skb_af, struct sk_buff *skb,
struct dst_entry *dst;
int mtu;
int local, noref = 1;
+ struct ipv6hdr *hdr = ipv6_hdr(skb);
if (dest) {
dest_dst = __ip_vs_dst_check(dest);
@@ -473,6 +489,19 @@ __ip_vs_get_out_rt_v6(struct netns_ipvs *ipvs, int
skb_af, struct sk_buff *skb,
return local;
}
+ /* check and decrement ttl */
+ if (hdr->hop_limit <= 1) {
+ /* Force OUTPUT device used as source address */
+ if (!dst)
+ dst = skb_dst(skb);
+ 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);
+
+ goto err_put;
+ }
+
/* MTU checking */
if (likely(!(rt_mode & IP_VS_RT_MODE_TUNNEL)))
mtu = dst_mtu(&rt->dst);
@@ -498,6 +527,11 @@ __ip_vs_get_out_rt_v6(struct netns_ipvs *ipvs, int
skb_af, struct sk_buff *skb,
} else
skb_dst_set(skb, &rt->dst);
+ /* don't propagate ttl change to cloned packets */
+ if (!skb_make_writable(skb, sizeof(struct ipv6hdr)))
+ goto err_put;
+
+ hdr->hop_limit--;
return local;
err_put:
@@ -739,9 +773,6 @@ ip_vs_nat_xmit(struct sk_buff *skb, struct
ip_vs_conn *cp,
}
/* copy-on-write the packet before mangling it */
- if (!skb_make_writable(skb, sizeof(struct iphdr)))
- goto tx_error;
-
if (skb_cow(skb, rt->dst.dev->hard_header_len))
goto tx_error;
@@ -831,9 +862,6 @@ ip_vs_nat_xmit_v6(struct sk_buff *skb, struct
ip_vs_conn *cp,
}
/* copy-on-write the packet before mangling it */
- if (!skb_make_writable(skb, sizeof(struct ipv6hdr)))
- goto tx_error;
-
if (skb_cow(skb, rt->dst.dev->hard_header_len))
goto tx_error;
@@ -1302,9 +1330,6 @@ ip_vs_icmp_xmit(struct sk_buff *skb, struct
ip_vs_conn *cp,
}
/* copy-on-write the packet before mangling it */
- if (!skb_make_writable(skb, offset))
- goto tx_error;
-
if (skb_cow(skb, rt->dst.dev->hard_header_len))
goto tx_error;
@@ -1394,9 +1419,6 @@ ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct
ip_vs_conn *cp,
}
/* copy-on-write the packet before mangling it */
- if (!skb_make_writable(skb, offset))
- goto tx_error;
-
if (skb_cow(skb, rt->dst.dev->hard_header_len))
goto tx_error;
--
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