From: Vadim Fedorenko vfedorenko@novek.ru
stable inclusion from linux-4.19.198 commit d76613a914b1950604bdcec2a44f4557ff42c65d
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[ Upstream commit fade56410c22cacafb1be9f911a0afd3701d8366 ]
Commit 14972cbd34ff ("net: lwtunnel: Handle fragmentation") moved fragmentation logic away from lwtunnel by carry encap headroom and use it in output MTU calculation. But the forwarding part was not covered and created difference in MTU for output and forwarding and further to silent drops on ipv4 forwarding path. Fix it by taking into account lwtunnel encap headroom.
The same commit also introduced difference in how to treat RTAX_MTU in IPv4 and IPv6 where latter explicitly removes lwtunnel encap headroom from route MTU. Make IPv4 version do the same.
Fixes: 14972cbd34ff ("net: lwtunnel: Handle fragmentation") Suggested-by: David Ahern dsahern@gmail.com Signed-off-by: Vadim Fedorenko vfedorenko@novek.ru Reviewed-by: David Ahern dsahern@kernel.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- include/net/ip.h | 12 ++++++++---- include/net/ip6_route.h | 16 ++++++++++++---- net/ipv4/route.c | 3 ++- 3 files changed, 22 insertions(+), 9 deletions(-)
diff --git a/include/net/ip.h b/include/net/ip.h index 17766586dfa09..26a8b622cd9cf 100644 --- a/include/net/ip.h +++ b/include/net/ip.h @@ -34,6 +34,7 @@ #include <net/flow.h> #include <net/flow_dissector.h> #include <net/netns/hash.h> +#include <net/lwtunnel.h>
#define IPV4_MAX_PMTU 65535U /* RFC 2675, Section 5.1 */ #define IPV4_MIN_MTU 68 /* RFC 791 */ @@ -408,22 +409,25 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
/* 'forwarding = true' case should always honour route mtu */ mtu = dst_metric_raw(dst, RTAX_MTU); - if (mtu) - return mtu; + if (!mtu) + mtu = min(READ_ONCE(dst->dev->mtu), IP_MAX_MTU);
- return min(READ_ONCE(dst->dev->mtu), IP_MAX_MTU); + return mtu - lwtunnel_headroom(dst->lwtstate, mtu); }
static inline unsigned int ip_skb_dst_mtu(struct sock *sk, const struct sk_buff *skb) { + unsigned int mtu; + if (!sk || !sk_fullsock(sk) || ip_sk_use_pmtu(sk)) { bool forwarding = IPCB(skb)->flags & IPSKB_FORWARDED;
return ip_dst_mtu_maybe_forward(skb_dst(skb), forwarding); }
- return min(READ_ONCE(skb_dst(skb)->dev->mtu), IP_MAX_MTU); + mtu = min(READ_ONCE(skb_dst(skb)->dev->mtu), IP_MAX_MTU); + return mtu - lwtunnel_headroom(skb_dst(skb)->lwtstate, mtu); }
int ip_metrics_convert(struct net *net, struct nlattr *fc_mx, int fc_mx_len, diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h index 5e26d61867b21..5c38a80cee3a2 100644 --- a/include/net/ip6_route.h +++ b/include/net/ip6_route.h @@ -243,11 +243,18 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
static inline int ip6_skb_dst_mtu(struct sk_buff *skb) { + int mtu; + struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ? inet6_sk(skb->sk) : NULL;
- return (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) ? - skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb)); + if (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) { + mtu = READ_ONCE(skb_dst(skb)->dev->mtu); + mtu -= lwtunnel_headroom(skb_dst(skb)->lwtstate, mtu); + } else + mtu = dst_mtu(skb_dst(skb)); + + return mtu; }
static inline bool ip6_sk_accept_pmtu(const struct sock *sk) @@ -288,7 +295,7 @@ static inline unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst) if (dst_metric_locked(dst, RTAX_MTU)) { mtu = dst_metric_raw(dst, RTAX_MTU); if (mtu) - return mtu; + goto out; }
mtu = IPV6_MIN_MTU; @@ -298,7 +305,8 @@ static inline unsigned int ip6_dst_mtu_forward(const struct dst_entry *dst) mtu = idev->cnf.mtu6; rcu_read_unlock();
- return mtu; +out: + return mtu - lwtunnel_headroom(dst->lwtstate, mtu); }
u32 ip6_mtu_from_fib6(struct fib6_info *f6i, struct in6_addr *daddr, diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 958df3427c34f..25a89b3b4c22f 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1313,7 +1313,7 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst) mtu = dst_metric_raw(dst, RTAX_MTU);
if (mtu) - return mtu; + goto out;
mtu = READ_ONCE(dst->dev->mtu);
@@ -1322,6 +1322,7 @@ static unsigned int ipv4_mtu(const struct dst_entry *dst) mtu = 576; }
+out: mtu = min_t(unsigned int, mtu, IP_MAX_MTU);
return mtu - lwtunnel_headroom(dst->lwtstate, mtu);