Herbert Xu wrote: > On Tue, Jul 09, 2024 at 11:53:21AM -0400, Willem de Bruijn wrote: > > > > > + /* Due to header grow, MSS needs to be downgraded. > > > + * There is BUG_ON When segment the frag_list with > > > + * head_frag true so linearize skb after downgrade > > > + * the MSS. > > > + */ > > This sounds completely wrong. You should never grow the TCP header > by changing gso_size. What is the usage-scenario for this? > > Think about it, if a router forwards a TCP packet, and ends up > growing its TCP header and then splits the packet into two, then > this router is brain-dead. This is an unfortunate feature, but already exists. It decreases gso_size to account for tunnel headers. For USO, we added BPF_F_ADJ_ROOM_FIXED_GSO to avoid this in better, newer users.
