> THIS PATCH IS VERY POSSIBLY WRONG! But if it is I want some feedback.
>
> Basically what I found was that if I added an iptables rule like so:
>
> iptables -A OUTPUT -p tcp --dport 80 -j DROP
>
> And then ran a web browser like links it would just hang on 'establishing
> connection.' I expected that the application would immediately, or at least
> very quickly, get notified that the connect failed. This waiting for timeout
> would be expected if something else dropped the SYN or if we were dropping the
> SYN/ACK packet coming back, but I figured if we knew we threw away the SYN we knew
> right away that the connection was denied and we should be able to indicate
> that to the application. Yes, I realize this is little different than if the
> SYN was dropped in the first network device, but it is different because we
> know what happened! We know that connect() call failed and that there isn't
> anything coming back.
>
> What I discovered was that we actually had 2 problems in making it possible.
> For userspace to quickly realize the connect failed. The first was a problem
> in the netfilter code which wasn't passing errors back up the stack correctly,
> due to what I believe to be a mistake in precedence rules.
>
>
http://marc.info/?l=netfilter-devel&m=128950262021804&w=2
>
> And the second was that tcp_connect() was just ignoring the return value from
> tcp_transmit_skb(). Maybe this was intentional but I really wish we could
> find out that connect failed long before the minutes long timeout. Once I
> fixed both of those issues I find that links gets denied (with EPERM)
> immediately when it calls connect(). Is this wrong? Is this bad to tell
> userspace more quickly what happened? Does passing this error code back up
> the stack here break something else? Why do some functions seem to pay
> attention to tcp_transmit_skb() return codes and some functions just ignore
> it? What do others think?
>
