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authorSabrina Dubroca <sd@queasysnail.net>2018-03-14 12:21:14 +0300
committerDavid S. Miller <davem@davemloft.net>2018-03-14 20:37:36 +0300
commitd52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 (patch)
tree27f31c7dc279232da5b67a307e8a2fde449ac098 /include/net/route.h
parent16c2e4db832da4b883b3ee8b9dc32d1ca115759a (diff)
downloadlinux-d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221.tar.xz
ipv4: lock mtu in fnhe when received PMTU < net.ipv4.route.min_pmtu
Prior to the rework of PMTU information storage in commit 2c8cec5c10bc ("ipv4: Cache learned PMTU information in inetpeer."), when a PMTU event advertising a PMTU smaller than net.ipv4.route.min_pmtu was received, we would disable setting the DF flag on packets by locking the MTU metric, and set the PMTU to net.ipv4.route.min_pmtu. Since then, we don't disable DF, and set PMTU to net.ipv4.route.min_pmtu, so the intermediate router that has this link with a small MTU will have to drop the packets. This patch reestablishes pre-2.6.39 behavior by splitting rtable->rt_pmtu into a bitfield with rt_mtu_locked and rt_pmtu. rt_mtu_locked indicates that we shouldn't set the DF bit on that path, and is checked in ip_dont_fragment(). One possible workaround is to set net.ipv4.route.min_pmtu to a value low enough to accommodate the lowest MTU encountered. Fixes: 2c8cec5c10bc ("ipv4: Cache learned PMTU information in inetpeer.") Signed-off-by: Sabrina Dubroca <sd@queasysnail.net> Reviewed-by: Stefano Brivio <sbrivio@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/route.h')
-rw-r--r--include/net/route.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/include/net/route.h b/include/net/route.h
index 40b870d58f38..20a92ca9e115 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -63,7 +63,8 @@ struct rtable {
__be32 rt_gateway;
/* Miscellaneous cached information */
- u32 rt_pmtu;
+ u32 rt_mtu_locked:1,
+ rt_pmtu:31;
u32 rt_table_id;