On 4/20/22 5:21 PM, Guillaume Nault wrote: > RTO_ONLINK is a flag that allows to reduce the scope of route lookups. > It's stored in a normally unused bit of the ->flowi4_tos field, in > struct flowi4. However it has several problems: > > * This bit is also used by ECN. Although ECN bits are supposed to be > cleared before doing a route lookup, it happened that some code > paths didn't properly sanitise their ->flowi4_tos. So this mechanism > is fragile and we had bugs in the past where ECN bits slipped in and > could end up being erroneously interpreted as RTO_ONLINK. > > * A dscp_t type was recently introduced to ensure ECN bits are cleared > during route lookups. ->flowi4_tos is the most important structure > field to convert, but RTO_ONLINK prevents such conversion, as dscp_t > mandates that ECN bits (where RTO_ONLINK is stored) be zero. > > Therefore we need to stop using RTO_ONLINK altogether. Fortunately > RTO_ONLINK isn't a necessity. Instead of passing a flag in ->flowi4_tos > to tell the route lookup function to restrict the scope, we can simply > initialise the scope correctly. > I believe the set looks ok. I think the fib test coverage in selftests could use more tests to cover tos.
