Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3279431E846 for ; Tue, 1 Sep 2026 00:21:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788222064; cv=none; b=ace2XfUoRXwfH158DLVFAeP/VIS2R9URTS5abhTvLeHXp3IwI/mOxDokT5sqp4P10YFzemwJGv0xx1NqoZo6NI1/WlusuUVDroPXtN8UKcmUaCerbsf7Jfhm5rxoETwn7yqB/5/wwnWLEgREl+IQl+kJDnubafhJRVCeMKLlQeI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788222064; c=relaxed/simple; bh=w3xpUYittUcI6DHC4O8u+0mWPweMCgfiwflVxw/HtJY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HShxxpZv5vAf8LHCABze1tTGBSWZk0uue7ARw8FGRxyqcfM2U7n/8ITRUIejdqOd0sUq8agoy8PzrpCZEx6yIWriGMTprECEwq72kBoZK3GzVMDQFl4u9H2d5rMZXWL/yvO9hKDden4Aiab+jxtNxyGi6ZC327AfizQobOCX/gg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WGPyEpEd; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WGPyEpEd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7AA001F00A3E; Tue, 1 Sep 2026 00:21:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788222063; bh=VZZICSaHGVccme/t9W6VyySRjQ4sc94iz0k3a8tqDms=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WGPyEpEdO32qWVG0tVM36IlnCX82KWA3Y6kd0yDCUtuPP5dgv0WKXffvZ454b1p7v SdlX12cv4FiPa+IrDrf7mzb82MKXx9aaAHgRXGVqstzDlqAaY8XX9Q1R/op+mq4efz RrWG3jKQ82dBkdAAEb4yhJ43wdKPL//ONPsunb+ht3AkBjq8n0/1aqtX7IskvOGG2r T2h98GBP9RVGjx2hSwpEzZveN123oLXw42wq+OczyzAvLKrIs/mn/v1h2ZuNcVcXT4 JOPm+rNxWQfxqKK6hPXnDlH4AinbDT0Qz9ISwS2VCjThcfPnmdZjtBmvcnzJlvx0zD iMVqz/s6StOZQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Eric Dumazet , Kuniyuki Iwashima , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.18.y 5/6] ipv4: use dst4_mtu() instead of dst_mtu() Date: Mon, 31 Aug 2026 20:20:56 -0400 Message-ID: <20260901002057.2024614-5-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260901002057.2024614-1-sashal@kernel.org> References: <2026083104-huddle-balancing-d57b@gregkh> <20260901002057.2024614-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Eric Dumazet [ Upstream commit fe8570186f100b6cc499b2f7705946baf1388cde ] 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 Stable-dep-of: 870a9e42ecc6 ("tcp: clamp route advmss to TCP_MIN_MSS") Signed-off-by: Sasha Levin --- 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 691d7b076c620..a66e1a7175e90 100644 --- a/net/ipv4/icmp.c +++ b/net/ipv4/icmp.c @@ -790,7 +790,7 @@ 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.opt.optlen; diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 47d24f74ed1b6..267ac4730b590 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -1303,7 +1303,7 @@ 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; @@ -1442,7 +1442,7 @@ 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 7d4f1face2e79..7af607f329ac3 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 c47d56576720f..4626dc46808f3 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 708b69cc2f56c..6f8d27035b6fe 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -373,7 +373,7 @@ 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; @@ -385,15 +385,14 @@ 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 @@ -1817,7 +1816,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb, #endif 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 c03df1682a639..77918643d1754 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -963,7 +963,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb, iph6 = ipv6_hdr(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