From: Eric Dumazet <edumazet@google.com>
To: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>, David Ahern <dsahern@kernel.org>,
Kuniyuki Iwashima <kuniyu@google.com>,
netdev@vger.kernel.org, eric.dumazet@gmail.com,
Eric Dumazet <edumazet@google.com>
Subject: [PATCH net-next 6/8] ipv6: use dst6_mtu() instead of dst_mtu()
Date: Fri, 30 Jan 2026 21:03:01 +0000 [thread overview]
Message-ID: <20260130210303.3888261-7-edumazet@google.com> (raw)
In-Reply-To: <20260130210303.3888261-1-edumazet@google.com>
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>
---
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(-)
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index d19d86ed43766bbc8ec052113be02ab231a5272c..dafcc0dcd77a5394857d6f339d83370826a25109 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -1057,7 +1057,7 @@ 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 4bb61265f1d8f870dbfd60bd22b8ab78828fb4cd..f110701d1eca1e5f763d9138a43e11e92c15412f 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);
@@ -1403,10 +1403,10 @@ 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 6fca0868b5a237417eb4c013f713952e8922696d..4c29aa94e86eb9439458e4b23426bfda8b3b8922 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -638,7 +638,7 @@ 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);
@@ -1187,7 +1187,7 @@ 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 a61e742794f9e67ff3743ddc31341d8647d5bcdc..d784a8644ff20e6008925b3d9b8e13c380318657 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -1184,7 +1184,7 @@ 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;
@@ -1283,7 +1283,7 @@ 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 3cfa7ae1294b59d14e030fb7a4ceabd4e9b673a8..c0350d97307e1ef6a3b500db32a311891d3c6e72 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2049,6 +2049,8 @@ 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.
@@ -2059,10 +2061,10 @@ 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;
@@ -2932,7 +2934,7 @@ 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)) {
@@ -3248,7 +3250,7 @@ EXPORT_SYMBOL_GPL(ip6_sk_redirect);
static unsigned int ip6_default_advmss(const struct dst_entry *dst)
{
- unsigned int mtu = dst_mtu(dst);
+ unsigned int mtu = dst6_mtu(dst);
struct net *net;
mtu -= sizeof(struct ipv6hdr) + sizeof(struct tcphdr);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 4ae664b05fa9171ed996bf8f3b6e7b2aaa63d5c9..f154d8720e64908083032df7d8645289e801a59d 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -351,7 +351,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *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;
@@ -368,8 +368,9 @@ 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);
}
}
@@ -1467,7 +1468,7 @@ 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.rc1.225.gd81095ad13-goog
next prev parent reply other threads:[~2026-01-30 21:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-30 21:02 [PATCH net-next 0/8] ipv6: misc changes in output path Eric Dumazet
2026-01-30 21:02 ` [PATCH net-next 1/8] ipv6: pass proto by value to ipv6_push_nfrag_opts() and ipv6_push_frag_opts() Eric Dumazet
2026-01-31 6:29 ` Kuniyuki Iwashima
2026-01-30 21:02 ` [PATCH net-next 2/8] ipv6: add some unlikely()/likely() clauses in ip6_output.c Eric Dumazet
2026-01-31 6:30 ` Kuniyuki Iwashima
2026-01-30 21:02 ` [PATCH net-next 3/8] ipv6: use __skb_push() in ip6_xmit() Eric Dumazet
2026-01-31 6:32 ` Kuniyuki Iwashima
2026-01-30 21:02 ` [PATCH net-next 4/8] ipv6: use SKB_DROP_REASON_PKT_TOO_BIG " Eric Dumazet
2026-01-31 6:33 ` Kuniyuki Iwashima
2026-01-30 21:03 ` [PATCH net-next 5/8] inet: add dst4_mtu() and dst6_mtu() helpers Eric Dumazet
2026-01-31 6:34 ` Kuniyuki Iwashima
2026-01-30 21:03 ` Eric Dumazet [this message]
2026-01-31 6:39 ` [PATCH net-next 6/8] ipv6: use dst6_mtu() instead of dst_mtu() Kuniyuki Iwashima
2026-01-30 21:03 ` [PATCH net-next 7/8] ipv4: use dst4_mtu() " Eric Dumazet
2026-01-31 6:42 ` Kuniyuki Iwashima
2026-01-30 21:03 ` [PATCH net-next 8/8] ipv6: colocate inet6_cork in inet_cork_full Eric Dumazet
2026-01-31 6:46 ` Kuniyuki Iwashima
2026-02-03 2:00 ` [PATCH net-next 0/8] ipv6: misc changes in output path patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260130210303.3888261-7-edumazet@google.com \
--to=edumazet@google.com \
--cc=davem@davemloft.net \
--cc=dsahern@kernel.org \
--cc=eric.dumazet@gmail.com \
--cc=horms@kernel.org \
--cc=kuba@kernel.org \
--cc=kuniyu@google.com \
--cc=netdev@vger.kernel.org \
--cc=pabeni@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox