17.01.2020 22:09, Victor Sudakov wrote: >>> Back to the point. I've figured out that both encrypted (in transport >>> mode) and unencrypted TCP segments have the same MSS=1460. Then I'm >>> completely at a loss how the encrypted packets avoid being fragmented. >>> TCP has no way to know in advance that encryption overhead will be >>> added. >> >> If outgoing route (f.e. default route) has lower MTU, kernel should respond >> with EMSGSIZE >> to TCP's attempt to send oversized packet when PMTUD is enabled. >> >> If PMTUD discovers that path mtu is low, it should store this information in >> the hostcache >> (see sysctl net.inet.tcp.hostcache.list) and use hostcache's MTU for same >> goal. > > Should this result in a smaller MSS in TCP to such hosts? > > PS "sysctl net.inet.tcp.hostcache.list | grep 192.168.246.11" yields > nothing, and yet 192.168.246.11 is the VM with which I have a transport > mode SA.
I guess that Path MTU in such case is 1500, so PMTUD won't help here. _______________________________________________ freebsd-net@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
