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ip/tcp: never raise the mss over the link mtu < 1280 for v6

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v6 mandates minimum mtu of 1280, tho someone *could* setup
an interface with a lower mtu or set it lower for testing.
This commit is contained in:
cinap_lenrek 2016-11-16 00:54:04 +01:00
parent 323d625864
commit 78d2a52577
1 changed files with 5 additions and 4 deletions
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9
sys/src/9/ip/tcp.c
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@ -864,13 +864,14 @@ tcpmtu(Route *r, int version, uint *scale)
* otherwise, we use the default MSS which assumes a
* safe minimum MTU of 1280 bytes for V6.
*/
if(r != nil && (version == V4 || (r->type & (Rifc|Runi)) != 0)){
if(r != nil){
ifc = r->ifc;
mtu = ifc->maxtu - ifc->m->hsize;
if(version == V6)
return mtu - (TCP6_PKT + TCP6_HDRSIZE);
else
if(version == V4)
return mtu - (TCP4_PKT + TCP4_HDRSIZE);
mtu -= TCP6_PKT + TCP6_HDRSIZE;
if((r->type & (Rifc|Runi)) != 0 || mtu <= DEF_MSS6)
return mtu;
}
if(version == V6)
return DEF_MSS6;