netdev - [RFC net-next 2/2] net: ipv4: Consolidate ipv4_mtu and ip_dst_mtu_maybe

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Message-Id: <20210701011728.22626-3-vfedorenko@novek.ru>
Date:   Thu,  1 Jul 2021 04:17:28 +0300
From:   Vadim Fedorenko <vfedorenko@...ek.ru>
To:     David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        "David S. Miller" <davem@...emloft.net>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Vadim Fedorenko <vfedorenko@...ek.ru>
Subject: [RFC net-next 2/2] net: ipv4: Consolidate ipv4_mtu and ip_dst_mtu_maybe_forward

Consolidate IPv4 MTU code the same way it is done in IPv6 to have code
aligned in both address families

Signed-off-by: Vadim Fedorenko <vfedorenko@...ek.ru>
---
 include/net/ip.h | 22 ++++++++++++++++++----
 net/ipv4/route.c | 21 +--------------------
 2 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index d9683bef8684..ed261f2a40ac 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -436,18 +436,32 @@ static inline bool ip_sk_ignore_df(const struct sock *sk)
 static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
 						    bool forwarding)
 {
+	const struct rtable *rt = (const struct rtable *)dst;
 	struct net *net = dev_net(dst->dev);
 	unsigned int mtu;
 
 	if (net->ipv4.sysctl_ip_fwd_use_pmtu ||
 	    ip_mtu_locked(dst) ||
-	    !forwarding)
-		return dst_mtu(dst);
+	    !forwarding) {
+		mtu = rt->rt_pmtu;
+		if (mtu && time_before(jiffies, rt->dst.expires))
+			goto out;
+	}
 
 	/* 'forwarding = true' case should always honour route mtu */
 	mtu = dst_metric_raw(dst, RTAX_MTU);
-	if (!mtu)
-		mtu = min(READ_ONCE(dst->dev->mtu), IP_MAX_MTU);
+	if (mtu)
+		goto out;
+
+	mtu = READ_ONCE(dst->dev->mtu);
+
+	if (unlikely(ip_mtu_locked(dst))) {
+		if (rt->rt_uses_gateway && mtu > 576)
+			mtu = 576;
+	}
+
+out:
+	mtu = min_t(unsigned int, mtu, IP_MAX_MTU);
 
 	return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
 }
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 99c06944501a..04754d55b3c1 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1299,26 +1299,7 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
 
 INDIRECT_CALLABLE_SCOPE unsigned int ipv4_mtu(const struct dst_entry *dst)
 {
-	const struct rtable *rt = (const struct rtable *)dst;
-	unsigned int mtu = rt->rt_pmtu;
-
-	if (!mtu || time_after_eq(jiffies, rt->dst.expires))
-		mtu = dst_metric_raw(dst, RTAX_MTU);
-
-	if (mtu)
-		goto out;
-
-	mtu = READ_ONCE(dst->dev->mtu);
-
-	if (unlikely(ip_mtu_locked(dst))) {
-		if (rt->rt_uses_gateway && mtu > 576)
-			mtu = 576;
-	}
-
-out:
-	mtu = min_t(unsigned int, mtu, IP_MAX_MTU);
-
-	return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
+	return ip_dst_mtu_maybe_forward(dst, false);
 }
 EXPORT_INDIRECT_CALLABLE(ipv4_mtu);
 
-- 
2.18.4