On Mon, 25 Jan 2021 22:10:10 +0200 Slava Bacherikov wrote: > Hi, I'd like to report a regression. Currently, if you create GRE > interface on the latest stable or LTS kernel (5.4 branch) with > unspecified remote destination it's MTU will be adjusted for header size > twice. For example: > > $ ip link add name test type gre local 127.0.0.32 > $ ip link show test | grep mtu > 27: test@NONE: <NOARP> mtu 1452 qdisc noop state DOWN mode DEFAULT group > default qlen 1000 > > or with FOU > > $ ip link add name test2 type gre local 127.0.0.32 encap fou > encap-sport auto encap-dport 6666 > $ ip link show test2 | grep mtu > 28: test2@NONE: <NOARP> mtu 1436 qdisc noop state DOWN mode DEFAULT > group default qlen 1000 > > The same happens with GUE too (MTU is 1428 instead of 1464). > As you can see that MTU in first case is 1452 (1500 - 24 - 24) and with > FOU it's 1436 (1500 - 32 - 32), GUE 1428 (1500 - 36 - 36). If remote > address is specified MTU is correct. > > This regression caused by fdafed459998e2be0e877e6189b24cb7a0183224 commit.
Cong is this one on your radar?
