On 1/5/22 08:19, Guillaume Nault wrote: > On Wed, Jan 05, 2022 at 03:48:42AM -0800, Eric Dumazet wrote: >> From: Eric Dumazet <edumazet@xxxxxxxxxx> >> >> It seems pretty clear ppp layer assumed user space >> would always be kind to provide enough data >> in their write() to a ppp device. >> >> This patch makes sure user provides at least >> 2 bytes. >> >> It adds PPP_PROTO_LEN macro that could replace >> in net-next many occurrences of hard-coded 2 value. > > The PPP header can be compressed to only 1 byte, but since 2 bytes is > assumed in several parts of the code, rejecting such packets in > ppp_xmit() is probably the best we can do. The only ones that can be compressed are those less than 0x0100, which are (intentionally) all network layer protocols. We should be getting only control protocol messages though the user-space interface, not network layer, so I'd say it's not just the best we can do, but indeed the right thing to do by design. -- James Carlson 42.703N 71.076W <carlsonj@xxxxxxxxxxxxxxx>
