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ipv6: use dst6_mtu() instead of dst_mtu()

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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>
This commit is contained in:
Eric Dumazet 2026-01-30 21:03:01 +00:00 • committed by Jakub Kicinski
parent 8776c4ef3a
commit b40f0130a2
6 changed files with 19 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

2
net/ipv6/ip6_gre.c
View file

@ -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,

6
net/ipv6/ip6_output.c
View file

@ -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)

4
net/ipv6/ip6_tunnel.c
View file

@ -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 @@ 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;

4
net/ipv6/ipv6_sockglue.c
View file

@ -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;

10
net/ipv6/route.c
View file

@ -2049,6 +2049,8 @@ 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.
@ -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);

9
net/ipv6/tcp_ipv6.c
View file

@ -351,7 +351,7 @@ 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;
@ -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);