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Message-ID: <20260130210303.3888261-8-edumazet@google.com>
Date: Fri, 30 Jan 2026 21:03:02 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, David Ahern <dsahern@...nel.org>,
Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 7/8] ipv4: use dst4_mtu() instead of dst_mtu()
When we expect an IPv4 dst, use dst4_mtu() instead of dst_mtu()
to save some code space.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/ipv4/icmp.c | 2 +-
net/ipv4/ip_output.c | 4 ++--
net/ipv4/ip_sockglue.c | 2 +-
net/ipv4/ipmr.c | 2 +-
net/ipv4/netfilter/nf_reject_ipv4.c | 2 +-
net/ipv4/tcp_ipv4.c | 13 ++++++-------
net/ipv6/sit.c | 2 +-
7 files changed, 13 insertions(+), 14 deletions(-)
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 19c9c838967f761a8b3a1b07cea5c5ec932bf12d..1d362a17a1c446e8d988162b164c5096a7f5d9dc 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -945,7 +945,7 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
/* RFC says return as much as we can without exceeding 576 bytes. */
- room = dst_mtu(&rt->dst);
+ room = dst4_mtu(&rt->dst);
if (room > 576)
room = 576;
room -= sizeof(struct iphdr) + icmp_param->replyopts.opt.optlen;
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 75fcb58795bbbd97d9544c05b245675ad1d1383a..e4790cc7b5c2ec7d6893d4141ca250ec05a4a2f5 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1300,7 +1300,7 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
return -EFAULT;
cork->fragsize = ip_sk_use_pmtu(sk) ?
- dst_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
+ dst4_mtu(&rt->dst) : READ_ONCE(rt->dst.dev->mtu);
if (!inetdev_valid_mtu(cork->fragsize))
return -ENETUNREACH;
@@ -1439,7 +1439,7 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
pmtudisc = READ_ONCE(inet->pmtudisc);
if (pmtudisc == IP_PMTUDISC_DO ||
pmtudisc == IP_PMTUDISC_PROBE ||
- (skb->len <= dst_mtu(&rt->dst) &&
+ (skb->len <= dst4_mtu(&rt->dst) &&
ip_dont_fragment(sk, &rt->dst)))
df = htons(IP_DF);
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 6d9c5c20b1c4f93bd54283b5aadbb9bc61c24685..c062d9519818024e01746eec20eb3c036226f77e 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1634,7 +1634,7 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname,
val = 0;
dst = sk_dst_get(sk);
if (dst) {
- val = dst_mtu(dst);
+ val = dst4_mtu(dst);
dst_release(dst);
}
if (!val)
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index ca9eaee4c2ef5f5cdc03608291ad1a0dc187d657..131382c388e95707f27dd7d43be9b9ee2f62c85d 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1895,7 +1895,7 @@ static int ipmr_prepare_xmit(struct net *net, struct mr_table *mrt,
return -1;
}
- if (skb->len+encap > dst_mtu(&rt->dst) && (ntohs(iph->frag_off) & IP_DF)) {
+ if (skb->len+encap > dst4_mtu(&rt->dst) && (ntohs(iph->frag_off) & IP_DF)) {
/* Do not fragment multicasts. Alas, IPv4 does not
* allow to send ICMP, so that packets will disappear
* to blackhole.
diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c
index fae4aa4a5f0955849c6a4ba85bc925c33cd9e102..fecf6621f679f9d435803a7bd522b38bf3de7ef4 100644
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -303,7 +303,7 @@ void nf_send_reset(struct net *net, struct sock *sk, struct sk_buff *oldskb,
goto free_nskb;
/* "Never happens" */
- if (nskb->len > dst_mtu(skb_dst(nskb)))
+ if (nskb->len > dst4_mtu(skb_dst(nskb)))
goto free_nskb;
nf_ct_attach(nskb, oldskb);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ffdf52fbf6463b41d7c712f3710b681ecdf6e2d7..349ae751f9d0ea4090627717719c5afc573260fc 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -374,7 +374,7 @@ void tcp_v4_mtu_reduced(struct sock *sk)
{
struct inet_sock *inet = inet_sk(sk);
struct dst_entry *dst;
- u32 mtu;
+ u32 mtu, dmtu;
if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))
return;
@@ -386,15 +386,14 @@ void tcp_v4_mtu_reduced(struct sock *sk)
/* Something is about to be wrong... Remember soft error
* for the case, if this connection will not able to recover.
*/
- if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
+ dmtu = dst4_mtu(dst);
+ if (mtu < dmtu && ip_dont_fragment(sk, dst))
WRITE_ONCE(sk->sk_err_soft, EMSGSIZE);
- mtu = dst_mtu(dst);
-
if (inet->pmtudisc != IP_PMTUDISC_DONT &&
ip_sk_accept_pmtu(sk) &&
- inet_csk(sk)->icsk_pmtu_cookie > mtu) {
- tcp_sync_mss(sk, mtu);
+ inet_csk(sk)->icsk_pmtu_cookie > dmtu) {
+ tcp_sync_mss(sk, dmtu);
/* Resend the TCP packet because it's
* clear that the old packet has been
@@ -1760,7 +1759,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
tcp_ca_openreq_child(newsk, dst);
- tcp_sync_mss(newsk, dst_mtu(dst));
+ tcp_sync_mss(newsk, dst4_mtu(dst));
newtp->advmss = tcp_mss_clamp(tcp_sk(sk), dst_metric_advmss(dst));
tcp_initialize_rcv_mss(newsk);
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index cf37ad9686e698bf781df84f348d89ea7160ec63..439c8a1c662520d1769c0a60a5e9ae2cc0196d15 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -962,7 +962,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
}
if (df) {
- mtu = dst_mtu(&rt->dst) - t_hlen;
+ mtu = dst4_mtu(&rt->dst) - t_hlen;
if (mtu < IPV4_MIN_MTU) {
DEV_STATS_INC(dev, collisions);
--
2.53.0.rc1.225.gd81095ad13-goog
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