[PATCH 3.2 219/221] ipvs: rerouting to local clients is not needed anymore

Ben Hutchings
2015-05-05T02:26:08Z

From: Julian Anastasov <ja@ssi.bg>

commit 579eb62ac35845686a7c4286c0a820b4eb1f96aa upstream.

commit f5a41847acc5 ("ipvs: move ip_route_me_harder for ICMP")
from 2.6.37 introduced ip_route_me_harder() call for responses to
local clients, so that we can provide valid rt_src after SNAT.
It was used by TCP to provide valid daddr for ip_send_reply().
After commit 0a5ebb8000c5 ("ipv4: Pass explicit daddr arg to
ip_send_reply()." from 3.0 this rerouting is not needed anymore
and should be avoided, especially in LOCAL_IN.

Fixes 3.12.33 crash in xfrm reported by Florian Wiessner:
"3.12.33 - BUG xfrm_selector_match+0x25/0x2f6"

Reported-by: Smart Weblications GmbH - Florian Wiessner <f.wiessner@smart-weblications.de>
Tested-by: Smart Weblications GmbH - Florian Wiessner <f.wiessner@smart-weblications.de>
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
---
net/netfilter/ipvs/ip_vs_core.c | 32 +++++++++++++++++++++-----------
1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index 6dc7d7d..d864aaf 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -662,16 +662,24 @@ static inline int ip_vs_gather_frags_v6(struct sk_buff *skb, u_int32_t user)
}
#endif

-static int ip_vs_route_me_harder(int af, struct sk_buff *skb)
+static int ip_vs_route_me_harder(int af, struct sk_buff *skb,
+ unsigned int hooknum)
{
+ if (!sysctl_snat_reroute(skb))
+ return 0;
+ /* Reroute replies only to remote clients (FORWARD and LOCAL_OUT) */
+ if (NF_INET_LOCAL_IN == hooknum)
+ return 0;
#ifdef CONFIG_IP_VS_IPV6
if (af == AF_INET6) {
- if (sysctl_snat_reroute(skb) && ip6_route_me_harder(skb) != 0)
+ struct dst_entry *dst = skb_dst(skb);
+
+ if (dst->dev && !(dst->dev->flags & IFF_LOOPBACK) &&
+ ip6_route_me_harder(skb) != 0)
return 1;
} else
#endif
- if ((sysctl_snat_reroute(skb) ||
- skb_rtable(skb)->rt_flags & RTCF_LOCAL) &&
+ if (!(skb_rtable(skb)->rt_flags & RTCF_LOCAL) &&
ip_route_me_harder(skb, RTN_LOCAL) != 0)
return 1;

@@ -782,7 +790,8 @@ static int handle_response_icmp(int af, struct sk_buff *skb,
union nf_inet_addr *snet,
__u8 protocol, struct ip_vs_conn *cp,
struct ip_vs_protocol *pp,
- unsigned int offset, unsigned int ihl)
+ unsigned int offset, unsigned int ihl,
+ unsigned int hooknum)
{
unsigned int verdict = NF_DROP;

@@ -812,7 +821,7 @@ static int handle_response_icmp(int af, struct sk_buff *skb,
#endif
ip_vs_nat_icmp(skb, pp, cp, 1);

- if (ip_vs_route_me_harder(af, skb))
+ if (ip_vs_route_me_harder(af, skb, hooknum))
goto out;

/* do the statistics and put it back */
@@ -908,7 +917,7 @@ static int ip_vs_out_icmp(struct sk_buff *skb, int *related,

snet.ip = iph->saddr;
return handle_response_icmp(AF_INET, skb, &snet, cih->protocol, cp,
- pp, offset, ihl);
+ pp, offset, ihl, hooknum);
}

#ifdef CONFIG_IP_VS_IPV6
@@ -985,7 +994,8 @@ static int ip_vs_out_icmp_v6(struct sk_buff *skb, int *related,

ipv6_addr_copy(&snet.in6, &iph->saddr);
return handle_response_icmp(AF_INET6, skb, &snet, cih->nexthdr, cp,
- pp, offset, sizeof(struct ipv6hdr));
+ pp, offset, sizeof(struct ipv6hdr),
+ hooknum);
}
#endif

@@ -1018,7 +1028,7 @@ static inline int is_tcp_reset(const struct sk_buff *skb, int nh_len)
*/
static unsigned int
handle_response(int af, struct sk_buff *skb, struct ip_vs_proto_data *pd,
- struct ip_vs_conn *cp, int ihl)
+ struct ip_vs_conn *cp, int ihl, unsigned int hooknum)
{
struct ip_vs_protocol *pp = pd->pp;

@@ -1056,7 +1066,7 @@ handle_response(int af, struct sk_buff *skb, struct ip_vs_proto_data *pd,
* if it came from this machine itself. So re-compute
* the routing information.
*/
- if (ip_vs_route_me_harder(af, skb))
+ if (ip_vs_route_me_harder(af, skb, hooknum))
goto drop;

IP_VS_DBG_PKT(10, af, pp, skb, 0, "After SNAT");
@@ -1169,7 +1179,7 @@ ip_vs_out(unsigned int hooknum, struct sk_buff *skb, int af)
cp = pp->conn_out_get(af, skb, &iph, iph.len, 0);

if (likely(cp))
- return handle_response(af, skb, pd, cp, iph.len);
+ return handle_response(af, skb, pd, cp, iph.len, hooknum);
if (sysctl_nat_icmp_send(net) &&
(pp->protocol == IPPROTO_TCP ||
pp->protocol == IPPROTO_UDP ||