diff options
| author | Sabrina Dubroca <sd@queasysnail.net> | 2018-03-14 10:21:14 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-30 07:49:04 +0200 |
| commit | 119bbaa6795a4f4aed46994cc7d9ab01989c87e3 (patch) | |
| tree | b87814c94eb83af0c0f0c31e516c21246e06ad22 /include | |
| parent | b29cfb8ae0a309b99251bb1286012ac5d77ce2e5 (diff) | |
ipv4: lock mtu in fnhe when received PMTU < net.ipv4.route.min_pmtu
[ Upstream commit d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 ]
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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/ip.h | 11 | ||||
| -rw-r--r-- | include/net/ip_fib.h | 1 | ||||
| -rw-r--r-- | include/net/route.h | 3 |
3 files changed, 12 insertions, 3 deletions
diff --git a/include/net/ip.h b/include/net/ip.h index 639398af273b..0530bcdbc212 100644 --- a/include/net/ip.h +++ b/include/net/ip.h @@ -279,6 +279,13 @@ int ip_decrease_ttl(struct iphdr *iph) return --iph->ttl; } +static inline int ip_mtu_locked(const struct dst_entry *dst) +{ + const struct rtable *rt = (const struct rtable *)dst; + + return rt->rt_mtu_locked || dst_metric_locked(dst, RTAX_MTU); +} + static inline int ip_dont_fragment(const struct sock *sk, const struct dst_entry *dst) { @@ -286,7 +293,7 @@ int ip_dont_fragment(const struct sock *sk, const struct dst_entry *dst) return pmtudisc == IP_PMTUDISC_DO || (pmtudisc == IP_PMTUDISC_WANT && - !(dst_metric_locked(dst, RTAX_MTU))); + !ip_mtu_locked(dst)); } static inline bool ip_sk_accept_pmtu(const struct sock *sk) @@ -312,7 +319,7 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst, struct net *net = dev_net(dst->dev); if (net->ipv4.sysctl_ip_fwd_use_pmtu || - dst_metric_locked(dst, RTAX_MTU) || + ip_mtu_locked(dst) || !forwarding) return dst_mtu(dst); diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h index bda1721e9622..3afb7c4c7098 100644 --- a/include/net/ip_fib.h +++ b/include/net/ip_fib.h @@ -56,6 +56,7 @@ struct fib_nh_exception { int fnhe_genid; __be32 fnhe_daddr; u32 fnhe_pmtu; + bool fnhe_mtu_locked; __be32 fnhe_gw; unsigned long fnhe_expires; struct rtable __rcu *fnhe_rth_input; diff --git a/include/net/route.h b/include/net/route.h index a3b9ef74a389..d2a92d94ff72 100644 --- a/include/net/route.h +++ b/include/net/route.h @@ -64,7 +64,8 @@ struct rtable { __be32 rt_gateway; /* Miscellaneous cached information */ - u32 rt_pmtu; + u32 rt_mtu_locked:1, + rt_pmtu:31; u32 rt_table_id; |