From e2ca690b657f4ca5c204fcc6470d462b776d73b3 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Fri, 9 Oct 2015 14:34:31 +0200 Subject: ipv4/icmp: redirect messages can use the ingress daddr as source This patch allows configuring how the source address of ICMP redirect messages is selected; by default the old behaviour is retained, while setting icmp_redirects_use_orig_daddr force the usage of the destination address of the packet that caused the redirect. The new behaviour fits closely the RFC 5798 section 8.1.1, and fix the following scenario: Two machines are set up with VRRP to act as routers out of a subnet, they have IPs x.x.x.1/24 and x.x.x.2/24, with VRRP holding on to x.x.x.254/24. If a host in said subnet needs to get an ICMP redirect from the VRRP router, i.e. to reach a destination behind a different gateway, the source IP in the ICMP redirect is chosen as the primary IP on the interface that the packet arrived at, i.e. x.x.x.1 or x.x.x.2. The host will then ignore said redirect, due to RFC 1122 section 3.2.2.2, and will continue to use the wrong next-op. Signed-off-by: Paolo Abeni Signed-off-by: David S. Miller --- net/ipv4/icmp.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'net/ipv4/icmp.c') diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 36e26977c908..f3c356b7c1f0 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -659,7 +659,9 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) */ saddr = iph->daddr; - if (!(rt->rt_flags & RTCF_LOCAL)) { + if (!((type == ICMP_REDIRECT) && + net->ipv4.sysctl_icmp_redirects_use_orig_daddr) && + !(rt->rt_flags & RTCF_LOCAL)) { struct net_device *dev = NULL; rcu_read_lock(); @@ -1222,6 +1224,11 @@ static int __net_init icmp_sk_init(struct net *net) net->ipv4.sysctl_icmp_ratemask = 0x1818; net->ipv4.sysctl_icmp_errors_use_inbound_ifaddr = 0; + /* Control paramerer - use the daddr of originating packets as saddr + * in redirect messages? + */ + net->ipv4.sysctl_icmp_redirects_use_orig_daddr = 0; + return 0; fail: -- cgit v1.2.3