net: ipv4: Refine the ipv4_default_advmss (7ed14d97) · Commits · 戴 / test

1. Don't get the metric RTAX_ADVMSS of dst. There are two reasons. 1) Its caller dst_metric_advmss has already invoke dst_metric_advmss before invoke default_advmss. 2) The ipv4_default_advmss is used to get the default mss, it should not try to get the metric like ip6_default_advmss. 2. Use sizeof(tcphdr)+sizeof(iphdr) instead of literal 40. 3. Define one new macro IPV4_MAX_PMTU instead of 65535 according to RFC 2675, section 5.1. Signed-off-by:

Gao Feng <fgao@ikuai8.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

include/net/ip.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -33,6 +33,8 @@
		#include <net/flow.h>
		#include <net/flow_dissector.h>

		#define IPV4_MAX_PMTU 65535U /* RFC 2675, Section 5.1 */

		struct sock;

		struct inet_skb_parm {

net/ipv4/route.c

+4 −8

Original line number	Diff line number	Diff line
		@@ -1250,15 +1250,11 @@ static void set_class_tag(struct rtable *rt, u32 tag)

		static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
		{
		unsigned int advmss = dst_metric_raw(dst, RTAX_ADVMSS);

		if (advmss == 0) {
		advmss = max_t(unsigned int, dst->dev->mtu - 40,
		unsigned int header_size = sizeof(struct tcphdr) + sizeof(struct iphdr);
		unsigned int advmss = max_t(unsigned int, dst->dev->mtu - header_size,
		ip_rt_min_advmss);
		if (advmss > 65535 - 40)
		advmss = 65535 - 40;
		}
		return advmss;

		return min(advmss, IPV4_MAX_PMTU - header_size);
		}

		static unsigned int ipv4_mtu(const struct dst_entry *dst)

Admin message