From 1dced6a854827eb5683f3c57ddbb4595daf145e4 Mon Sep 17 00:00:00 2001 From: =?utf8?q?S=C3=A9bastien=20Barr=C3=A9?= Date: Sun, 17 Aug 2014 09:19:54 +0200 Subject: [PATCH] ipv4: Restore accept_local behaviour in fib_validate_source() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Commit 7a9bc9b81a5b ("ipv4: Elide fib_validate_source() completely when possible.") introduced a short-circuit to avoid calling fib_validate_source when not needed. That change took rp_filter into account, but not accept_local. This resulted in a change of behaviour: with rp_filter and accept_local off, incoming packets with a local address in the source field should be dropped. Here is how to reproduce the change pre/post 7a9bc9b81a5b commit: -configure the same IPv4 address on hosts A and B. -try to send an ARP request from B to A. -The ARP request will be dropped before that commit, but accepted and answered after that commit. This adds a check for ACCEPT_LOCAL, to maintain full fib validation in case it is 0. We also leave __fib_validate_source() earlier when possible, based on the same check as fib_validate_source(), once the accept_local stuff is verified. Cc: Gregory Detal Cc: Christoph Paasch Cc: Hannes Frederic Sowa Cc: Sergei Shtylyov Signed-off-by: Sébastien Barré Signed-off-by: David S. Miller --- net/ipv4/fib_frontend.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c index 255aa9946fe7..23104a3f2924 100644 --- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -243,7 +243,7 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst, u8 tos, int oif, struct net_device *dev, int rpf, struct in_device *idev, u32 *itag) { - int ret, no_addr, accept_local; + int ret, no_addr; struct fib_result res; struct flowi4 fl4; struct net *net; @@ -258,16 +258,17 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst, no_addr = idev->ifa_list == NULL; - accept_local = IN_DEV_ACCEPT_LOCAL(idev); fl4.flowi4_mark = IN_DEV_SRC_VMARK(idev) ? skb->mark : 0; net = dev_net(dev); if (fib_lookup(net, &fl4, &res)) goto last_resort; - if (res.type != RTN_UNICAST) { - if (res.type != RTN_LOCAL || !accept_local) - goto e_inval; - } + if (res.type != RTN_UNICAST && + (res.type != RTN_LOCAL || !IN_DEV_ACCEPT_LOCAL(idev))) + goto e_inval; + if (!rpf && !fib_num_tclassid_users(dev_net(dev)) && + (dev->ifindex != oif || !IN_DEV_TX_REDIRECTS(idev))) + goto last_resort; fib_combine_itag(itag, &res); dev_match = false; @@ -321,6 +322,7 @@ int fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst, int r = secpath_exists(skb) ? 0 : IN_DEV_RPFILTER(idev); if (!r && !fib_num_tclassid_users(dev_net(dev)) && + IN_DEV_ACCEPT_LOCAL(idev) && (dev->ifindex != oif || !IN_DEV_TX_REDIRECTS(idev))) { *itag = 0; return 0; -- 2.20.1