[PATCH 6.12 0967/1102] ipv6: use dst6_mtu() instead of dst_mtu()
flat view
COLD20d
REVIEWED: 3 (3M)
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2026-09-17 18:58:45
Also in:
linux-patches
1 review trailer.
6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet <redacted> [ 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 <redacted> Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com> Link: https://patch.msgid.link/20260130210303.3888261-7-edumazet@google.com (local) Signed-off-by: Jakub Kicinski <kuba@kernel.org> [ Adapted the net/ipv6/route.c hunk in ip6_default_advmss(): this tree already refactors that function to pull dst_dev(dst) into a local `dev` variable ahead of the mtu line, a shape upstream's hunk context didn't anticipate. Kept that `dev` line as-is and applied the dst_mtu() -> dst6_mtu() conversion to the mtu line, same as upstream. ] Stable-dep-of: 870a9e42ecc6 ("tcp: clamp route advmss to TCP_MIN_MSS") Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 | 10 ++++++---- net/ipv6/tcp_ipv6.c | 9 +++++---- 6 files changed, 19 insertions(+), 16 deletions(-)
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c@@ -1090,7 +1090,7 @@ static netdev_tx_t ip6erspan_tunnel_xmit /* 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, --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c
@@ -353,7 +353,7 @@ int ip6_xmit(const struct sock *sk, stru 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 *s 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) --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c
@@ -643,7 +643,7 @@ ip4ip6_err(struct sk_buff *skb, struct i /* 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 @@ route_lookup: 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; --- a/net/ipv6/ipv6_sockglue.c +++ b/net/ipv6/ipv6_sockglue.c
@@ -1195,7 +1195,7 @@ int do_ipv6_getsockopt(struct sock *sk, 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;
@@ -1294,7 +1294,7 @@ int do_ipv6_getsockopt(struct sock *sk, 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; --- a/net/ipv6/route.c +++ b/net/ipv6/route.c
@@ -2051,6 +2051,8 @@ unlock: 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 * 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;
@@ -2930,7 +2932,7 @@ static void __ip6_rt_update_pmtu(struct if (mtu < IPV6_MIN_MTU) return; - if (mtu >= dst_mtu(dst)) + if (mtu >= dst6_mtu(dst)) return; if (!rt6_cache_allowed_for_pmtu(rt6)) {
@@ -3248,7 +3250,7 @@ EXPORT_SYMBOL_GPL(ip6_sk_redirect); static unsigned int ip6_default_advmss(const struct dst_entry *dst) { struct net_device *dev = dst_dev(dst); - unsigned int mtu = dst_mtu(dst); + unsigned int mtu = dst6_mtu(dst); struct net *net; mtu -= sizeof(struct ipv6hdr) + sizeof(struct tcphdr); --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c
@@ -347,7 +347,7 @@ failure: 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 so 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); } }
@@ -1487,7 +1488,7 @@ static struct sock *tcp_v6_syn_recv_sock 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);