From: Eric Dumazet Date: Fri, 30 Jan 2026 21:03:02 +0000 (+0000) Subject: ipv4: use dst4_mtu() instead of dst_mtu() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fe8570186f100b6cc499b2f7705946baf1388cde;p=thirdparty%2Fkernel%2Flinux.git 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 Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260130210303.3888261-8-edumazet@google.com Signed-off-by: Jakub Kicinski --- diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c index 19c9c838967f7..1d362a17a1c44 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 75fcb58795bbb..e4790cc7b5c2e 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 6d9c5c20b1c4f..c062d95198180 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 ca9eaee4c2ef5..131382c388e95 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 fae4aa4a5f095..fecf6621f679f 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 0fc8a42921aab..01fd563472608 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 cf37ad9686e69..439c8a1c66252 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);