path: root/net
diff options
authorJulian Anastasov <ja@ssi.bg>2012-11-22 23:04:14 +0200
committerDavid S. Miller <davem@davemloft.net>2012-11-22 16:06:49 -0500
commit636174219b52b5a8bc51bc23bbcba97cd30a65e3 (patch)
treec2409e04422664285fe2a6774885d3d049d5d540 /net
parent84ec95b047d2d02552f07c06d9d6da8b61532090 (diff)
ipv4: do not cache looped multicasts
Starting from 3.6 we cache output routes for multicasts only when using route to 224/4. For local receivers we can set RTCF_LOCAL flag depending on the membership but in such case we use maddr and saddr which are not caching keys as before. Additionally, we can not use same place to cache routes that differ in RTCF_LOCAL flag value. Fix it by caching only RTCF_MULTICAST entries without RTCF_LOCAL (send-only, no loopback). As a side effect, we avoid unneeded lookup for fnhe when not caching because multicasts are not redirected and they do not learn PMTU. Thanks to Maxime Bizon for showing the caching problems in __mkroute_output for 3.6 kernels: different RTCF_LOCAL flag in cache can lead to wrong ip_mc_output or ip_output call and the visible problem is that traffic can not reach local receivers via loopback. Reported-by: Maxime Bizon <mbizon@freebox.fr> Tested-by: Maxime Bizon <mbizon@freebox.fr> Signed-off-by: Julian Anastasov <ja@ssi.bg> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
1 files changed, 5 insertions, 2 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 200d287e49f..df251424d81 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1785,6 +1785,7 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
if (dev_out->flags & IFF_LOOPBACK)
flags |= RTCF_LOCAL;
+ do_cache = true;
if (type == RTN_BROADCAST) {
fi = NULL;
@@ -1793,6 +1794,8 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
if (!ip_check_mc_rcu(in_dev, fl4->daddr, fl4->saddr,
flags &= ~RTCF_LOCAL;
+ else
+ do_cache = false;
/* If multicast route do not exist use
* default one, but do not gateway in this case.
* Yes, it is hack.
@@ -1802,8 +1805,8 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
fnhe = NULL;
- do_cache = fi != NULL;
- if (fi) {
+ do_cache &= fi != NULL;
+ if (do_cache) {
struct rtable __rcu **prth;
struct fib_nh *nh = &FIB_RES_NH(*res);