From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Eric Dumazet <edumazet@google.com>,
Kuniyuki Iwashima <kuniyu@google.com>,
Jakub Kicinski <kuba@kernel.org>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.12.y 4/5] ipv6: use dst6_mtu() instead of dst_mtu()
Date: Tue, 1 Sep 2026 07:11:14 -0400 [thread overview]
Message-ID: <20260901111115.4175900-4-sashal@kernel.org> (raw)
In-Reply-To: <20260901111115.4175900-1-sashal@kernel.org>
From: Eric Dumazet <edumazet@google.com>
[ Upstream commit b40f0130a23b6bab8b359e158a40af81f11f14be ]
When we expect an IPv6 dst, use dst6_mtu() instead of dst_mtu()
to save some code space.
Due to current dst6_mtu() implementation, only convert
users in IPv6 stack.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260130210303.3888261-7-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 2640e6419594 ("net: advertise TCP MSS from the configured MTU, not the learned PMTU")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/ip6_gre.c | 2 +-
net/ipv6/ip6_output.c | 6 +++---
net/ipv6/ip6_tunnel.c | 4 ++--
net/ipv6/ipv6_sockglue.c | 4 ++--
net/ipv6/route.c | 8 +++++---
net/ipv6/tcp_ipv6.c | 9 +++++----
6 files changed, 18 insertions(+), 15 deletions(-)
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index dac2e589849df..cf7e5d1046672 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -1086,7 +1086,7 @@ static netdev_tx_t ip6erspan_tunnel_xmit(struct sk_buff *skb,
/* TooBig packet may have updated dst->dev's mtu */
if (!t->parms.collect_md && dst) {
mtu = READ_ONCE(dst_dev(dst)->mtu);
- if (dst_mtu(dst) > mtu)
+ if (dst6_mtu(dst) > mtu)
dst->ops->update_pmtu(dst, NULL, skb, mtu, false);
}
err = ip6_tnl_xmit(skb, dev, dsfield, &fl6, encap_limit, &mtu,
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index c1227bfeb8496..e483ea209fb76 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -353,7 +353,7 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
skb->priority = priority;
skb->mark = mark;
- mtu = dst_mtu(dst);
+ mtu = dst6_mtu(dst);
if (likely((skb->len <= mtu) || skb->ignore_df || skb_is_gso(skb))) {
IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTREQUESTS);
@@ -1400,10 +1400,10 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
v6_cork->dontfrag = ipc6->dontfrag;
if (rt->dst.flags & DST_XFRM_TUNNEL)
mtu = READ_ONCE(np->pmtudisc) >= IPV6_PMTUDISC_PROBE ?
- READ_ONCE(rt->dst.dev->mtu) : dst_mtu(&rt->dst);
+ READ_ONCE(rt->dst.dev->mtu) : dst6_mtu(&rt->dst);
else
mtu = READ_ONCE(np->pmtudisc) >= IPV6_PMTUDISC_PROBE ?
- READ_ONCE(rt->dst.dev->mtu) : dst_mtu(xfrm_dst_path(&rt->dst));
+ READ_ONCE(rt->dst.dev->mtu) : dst6_mtu(xfrm_dst_path(&rt->dst));
frag_size = READ_ONCE(np->frag_size);
if (frag_size && frag_size < mtu)
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 43ccc1a0a0d04..60b2583a8b2b4 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -643,7 +643,7 @@ ip4ip6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
/* change mtu on this route */
if (rel_type == ICMP_DEST_UNREACH && rel_code == ICMP_FRAG_NEEDED) {
- if (rel_info > dst_mtu(skb_dst(skb2)))
+ if (rel_info > dst6_mtu(skb_dst(skb2)))
goto out;
skb_dst_update_pmtu_no_confirm(skb2, rel_info);
@@ -1195,7 +1195,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
t->parms.name);
goto tx_err_dst_release;
}
- mtu = dst_mtu(dst) - eth_hlen - psh_hlen - t->tun_hlen;
+ mtu = dst6_mtu(dst) - eth_hlen - psh_hlen - t->tun_hlen;
if (encap_limit >= 0) {
max_headroom += 8;
mtu -= 8;
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 1e225e6489ea1..c2ea92c0f9166 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -1204,7 +1204,7 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
rcu_read_lock();
dst = __sk_dst_get(sk);
if (dst)
- val = dst_mtu(dst);
+ val = dst6_mtu(dst);
rcu_read_unlock();
if (!val)
return -ENOTCONN;
@@ -1303,7 +1303,7 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
rcu_read_lock();
dst = __sk_dst_get(sk);
if (dst)
- mtuinfo.ip6m_mtu = dst_mtu(dst);
+ mtuinfo.ip6m_mtu = dst6_mtu(dst);
rcu_read_unlock();
if (!mtuinfo.ip6m_mtu)
return -ENOTCONN;
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index eb2ba7c34f6f8..f7a138e317bad 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2051,6 +2051,8 @@ static void rt6_update_exception_stamp_rt(struct rt6_info *rt)
static bool rt6_mtu_change_route_allowed(struct inet6_dev *idev,
struct rt6_info *rt, int mtu)
{
+ u32 dmtu = dst6_mtu(&rt->dst);
+
/* If the new MTU is lower than the route PMTU, this new MTU will be the
* lowest MTU in the path: always allow updating the route PMTU to
* reflect PMTU decreases.
@@ -2061,10 +2063,10 @@ static bool rt6_mtu_change_route_allowed(struct inet6_dev *idev,
* handle this.
*/
- if (dst_mtu(&rt->dst) >= mtu)
+ if (dmtu >= mtu)
return true;
- if (dst_mtu(&rt->dst) == idev->cnf.mtu6)
+ if (dmtu == idev->cnf.mtu6)
return true;
return false;
@@ -2927,7 +2929,7 @@ static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,
if (mtu < IPV6_MIN_MTU)
return;
- if (mtu >= dst_mtu(dst))
+ if (mtu >= dst6_mtu(dst))
return;
if (!rt6_cache_allowed_for_pmtu(rt6)) {
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 085fc97c5a5b3..b6190f09551d5 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -347,7 +347,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
static void tcp_v6_mtu_reduced(struct sock *sk)
{
struct dst_entry *dst;
- u32 mtu;
+ u32 mtu, dmtu;
if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))
return;
@@ -364,8 +364,9 @@ static void tcp_v6_mtu_reduced(struct sock *sk)
if (!dst)
return;
- if (inet_csk(sk)->icsk_pmtu_cookie > dst_mtu(dst)) {
- tcp_sync_mss(sk, dst_mtu(dst));
+ dmtu = dst6_mtu(dst);
+ if (inet_csk(sk)->icsk_pmtu_cookie > dmtu) {
+ tcp_sync_mss(sk, dmtu);
tcp_simple_retransmit(sk);
}
}
@@ -1500,7 +1501,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
tcp_ca_openreq_child(newsk, dst);
- tcp_sync_mss(newsk, dst_mtu(dst));
+ tcp_sync_mss(newsk, dst6_mtu(dst));
newtp->advmss = tcp_mss_clamp(tcp_sk(sk), dst_metric_advmss(dst));
tcp_initialize_rcv_mss(newsk);
--
2.53.0
next prev parent reply other threads:[~2026-09-01 11:11 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-31 12:52 FAILED: patch "[PATCH] net: advertise TCP MSS from the configured MTU, not the" failed to apply to 6.12-stable tree gregkh
2026-09-01 11:11 ` [PATCH 6.12.y 1/5] ipv6: start using dst_dev_rcu() Sasha Levin
2026-09-01 11:11 ` [PATCH 6.12.y 2/5] ipv6: pass proto by value to ipv6_push_nfrag_opts() and ipv6_push_frag_opts() Sasha Levin
2026-09-01 11:11 ` [PATCH 6.12.y 3/5] ipv6: add some unlikely()/likely() clauses in ip6_output.c Sasha Levin
2026-09-01 11:11 ` Sasha Levin [this message]
2026-09-01 11:11 ` [PATCH 6.12.y 5/5] net: advertise TCP MSS from the configured MTU, not the learned PMTU Sasha Levin
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