On Tue, Nov 26, 2019 at 08:03 PM CET, Martin Lau wrote: > On Tue, Nov 26, 2019 at 03:30:57PM +0100, Jakub Sitnicki wrote: >> On Mon, Nov 25, 2019 at 11:07 PM CET, Martin Lau wrote: >> > On Mon, Nov 25, 2019 at 11:40:41AM +0100, Jakub Sitnicki wrote: [...] >> I agree, it's not obvious. When I first saw this check in >> reuseport_array_update_check it got me puzzled too. I should have added >> an explanatory comment there. >> >> Thing is we're not matching on just TCP_LISTEN. REUSEPORT_SOCKARRAY >> allows selecting a connected UDP socket as a target as well. It takes >> some effort to set up but it's possible even if obscure. > How about this instead: > if (!reuse) > /* reuseport_array only has sk that has non NULL sk_reuseport_cb. > * The only (!reuse) case here is, the sk has already been removed from > * reuseport_array, so treat it as -ENOENT. > * > * Other maps (e.g. sock_map) do not provide this guarantee and the sk may > * never be in the reuseport to begin with. > */ > return map->map_type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY ? -ENOENT : -EINVAL; Right, apart from established TCP sockets we must not select a listening socket that's not in a reuseport group either. This covers both cases. Clever. Thanks for the suggestion. > >> >> > Note that the SOCK_RCU_FREE check at the 'slow-path' >> > reuseport_array_update_check() is because reuseport_array does depend on >> > call_rcu(&sk->sk_rcu,...) to work, e.g. the reuseport_array >> > does not hold the sk_refcnt. >> >> Oh, so it's not only about socket state like I thought. >> >> This raises the question - does REUSEPORT_SOCKARRAY allow storing >> connected UDP sockets by design or is it a happy accident? It doesn't >> seem particularly useful. > Not by design/accident on the REUSEPORT_SOCKARRAY side ;) > > The intention of REUSEPORT_SOCKARRAY is to allow sk that can be added to > reuse->socks[]. Ah, makes sense. REUSEPORT_SOCKARRAY had to mimic reuseport groups. -Jakub
