Gur Stavi wrote:
Gur Stavi wrote:
Gur Stavi wrote:
Gur Stavi wrote: > > Gur Stavi wrote: > > > >> @@ -1846,21 +1846,21 @@ static int fanout_add(struct
sock
*sk,
> > struct fanout_args *args) > > > >> err = -EINVAL; > > > >> > > > >> spin_lock(&po->bind_lock); > > > >> - if (packet_sock_flag(po, PACKET_SOCK_RUNNING) && > > > >> - match->type == type && > > > >> + if (match->type == type && > > > >> match->prot_hook.type == po->prot_hook.type && > > > >> match->prot_hook.dev == po->prot_hook.dev) { > > > > > > > > Remaining unaddressed issue is that the socket can now be
added
> > > > before being bound. See comment in v1. > > > > > > I extended the psock_fanout test with unbound fanout test. > > > > > > As far as I understand, the easiest way to verify bind is
to
test
that > > > po->prot_hook.dev != NULL, since we are under a bind_lock
anyway.
> > > But perhaps a more readable and direct approach to test
"bind"
would be > > > to test po->ifindex != -1, as ifindex is commented as
"bound
device". > > > However, at the moment ifindex is not initialized to -1, I
can
add
such > > > initialization, but perhaps I do not fully understand all
the
logic. > > > > > > Any preferences? > > > > prot_hook.dev is not necessarily set if a packet socket is
bound.
> > It may be bound to any device. See dev_add_pack and
ptype_head.
> > > > prot_hook.type, on the other hand, must be set if bound and
is
only
> > modified with the bind_lock held too. > > > > Well, and in packet_create. But setsockopt PACKET_FANOUT_ADD
also
> > succeeds in case bind() was not called explicitly first to
bind
to
> > a specific device or change ptype. > > Please clarify the last paragraph? When you say "also succeeds"
do
you
> mean SHOULD succeed or MAY SUCCEED by mistake if "something"
happens
???
I mean it succeeds currently. Which behavior must then be
maintained.
> Do you refer to the following scenario: socket is created with
non-
zero
> protocol and becomes RUNNING "without bind" for all devices. In
that
case > it can be added to FANOUT without bind. Is that considered a
bug or
does > the bind requirement for fanout only apply for all-protocol (0) sockets?
I'm beginning to think that this bind requirement is not needed.
I agree with that. I think that is an historical mistake that
socket
becomes implicitly bound to all interfaces if a protocol is defined during create. Without this bind requirement would make sense.
All type and dev are valid, even if an ETH_P_NONE fanout group
would
be fairly useless.
Fanout is all about RX, I think that refusing fanout for socket
that
will not receive any packet is OK. The condition can be: if (po->ifindex == -1 || !po->num)
Fanout is not limited to sockets bound to a specific interface. This will break existing users.
For specific interface ifindex >= 1 For "any interface" ifindex == 0 ifindex is -1 only if the socket was created unbound with proto == 0 or for the rare race case that during re-bind the new dev became
unlisted.
For both of these cases fanout should fail.
The only case where packet_create does not call __register_prot_hook is if proto == 0. If proto is anything else, the socket will be bound, whether to a device hook, or ptype_all. I don't think we need this extra ifindex condition.
Even though "unbound" is an unlikely state for such a socket the code Should still address this state consistently. If do_bind sets ifindex to -1 on the unlikely unlisted scenario so should packet_create on the more likely proto == 0 scenario.
do_bind sets it to -1 for unlisted probably to copy existing behavior in packet_notifier on NETDEV_DOWN.
But as far as I can tell nothing that uses po->ifindex differentiates between 0 and -1. It just means that no actual device ifindex matches.
Binding to ETH_P_NONE is useless, but we're not going to slow down legitimate users with branches for cases that are harmless.
With "branch", do you refer to performance or something else? As I said in other mail, ETH_P_NONE could not be used in a fanout before as well because socket cannot become RUNNING with proto == 0.
Good point.
For performance, we removed the RUNNING condition and added this. It is not like we need to perform 5M fanout registrations/sec. It is a syscall after all.
It's as much about code complexity as performance. Both the patch and resulting code should be as small and self-evident as possible.
Patch v3 introduces a lot of code churn.
Did you look at a side by side comparison?
Obviously
There is really very little extra code.
1 file changed, 21 insertions(+), 14 deletions(-)
vs
1 file changed, 5 insertions(+), 5 deletions(-)
for v2.
If we don't care about opening up fanout groups to ETH_P_NONE, then patch v2 seems sufficient. If explicitly blocking this, the ENXIO return can be added, but ideally without touching the other lines.
I am not the one to decide if opening it is a good idea but it will be ironic if a patch with the intention to remove the only-RUNNING restriction will end up allowing never-RUNNING sockets into a fanout group.
It's fine to catch that, seem to just be this change?
spin_lock(&po->bind_lock); - if (po->running && + if (po->num != ETH_P_NONE && match->type == type && match->prot_hook.type == po->prot_hook.type && match->prot_hook.dev == po->prot_hook.dev) {