On Wed, Jan 27, 2021 at 4:56 PM Jakub Kicinski <k...@kernel.org> wrote: > > 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?
Yeah, I guess ipgre_link_update() somehow gets called twice, but I will need to look into it. Thanks.
