> -----Original Message----- > From: Joe Perches [mailto:j...@perches.com] > Sent: Wednesday, April 12, 2017 10:03 AM > To: gfree.w...@foxmail.com; da...@davemloft.net; kuz...@ms2.inr.ac.ru; > jmor...@namei.org; netdev@vger.kernel.org > Cc: Gao Feng <f...@ikuai8.com> > Subject: Re: [PATCH net-next 1/1] net: ipv4: Refine the ipv4_default_advmss > > On Wed, 2017-04-12 at 09:36 +0800, gfree.w...@foxmail.com wrote: > > From: Gao Feng <f...@ikuai8.com> > > > > 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. > > trivia: > > > diff --git a/net/ipv4/route.c b/net/ipv4/route.c > [] > > @@ -1250,14 +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); > > + 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 == 0) { > > - advmss = max_t(unsigned int, dst->dev->mtu - 40, > > - ip_rt_min_advmss); > > - if (advmss > 65535 - 40) > > - advmss = 65535 - 40; > > - } > > + advmss = min_t(unsigned int, advmss, IPV4_MAX_PMTU - header_size); > > as all the elements are now unsigned int, the min_t cast seems unnecessary.
Thanks, it is unnecessary to use min_t. I have corrected it now. Best Regards Feng
