ipv4: Don't use the cached pmtu informations for input routes (261663b0) · Commits · 戴 / test

The pmtu informations on the inetpeer are visible for output and input routes. On packet forwarding, we might propagate a learned pmtu to the sender. As we update the pmtu informations of the inetpeer on demand, the original sender of the forwarded packets might never notice when the pmtu to that inetpeer increases. So use the mtu of the outgoing device on packet forwarding instead of the pmtu to the final destination. Signed-off-by:

Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/route.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -1816,15 +1816,15 @@ static unsigned int ipv4_default_advmss(const struct dst_entry *dst)

	static unsigned int ipv4_mtu(const struct dst_entry *dst)		static unsigned int ipv4_mtu(const struct dst_entry *dst)
	{		{
			const struct rtable rt = (const struct rtable ) dst;
	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);		unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);

	if (mtu)		if (mtu && rt_is_output_route(rt))
	return mtu;		return mtu;

	mtu = dst->dev->mtu;		mtu = dst->dev->mtu;

	if (unlikely(dst_metric_locked(dst, RTAX_MTU))) {		if (unlikely(dst_metric_locked(dst, RTAX_MTU))) {
	const struct rtable rt = (const struct rtable ) dst;

	if (rt->rt_gateway != rt->rt_dst && mtu > 576)		if (rt->rt_gateway != rt->rt_dst && mtu > 576)
	mtu = 576;		mtu = 576;

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