net: ipv4: Refine the ipv4_default_advmss
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>
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@ -33,6 +33,8 @@
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#include <net/flow.h>
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#include <net/flow.h>
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#include <net/flow_dissector.h>
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#include <net/flow_dissector.h>
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#define IPV4_MAX_PMTU 65535U /* RFC 2675, Section 5.1 */
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struct sock;
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struct sock;
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struct inet_skb_parm {
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struct inet_skb_parm {
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@ -1250,15 +1250,11 @@ static void set_class_tag(struct rtable *rt, u32 tag)
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static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
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static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
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{
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{
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unsigned int advmss = dst_metric_raw(dst, RTAX_ADVMSS);
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unsigned int header_size = sizeof(struct tcphdr) + sizeof(struct iphdr);
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unsigned int advmss = max_t(unsigned int, dst->dev->mtu - header_size,
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ip_rt_min_advmss);
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if (advmss == 0) {
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return min(advmss, IPV4_MAX_PMTU - header_size);
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advmss = max_t(unsigned int, dst->dev->mtu - 40,
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ip_rt_min_advmss);
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if (advmss > 65535 - 40)
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advmss = 65535 - 40;
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}
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return advmss;
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}
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}
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static unsigned int ipv4_mtu(const struct dst_entry *dst)
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static unsigned int ipv4_mtu(const struct dst_entry *dst)
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