Messages in this thread | | | Subject | Re: [RFC PATCH] network: return errors if we know tcp_connect failed | From | Eric Paris <> | Date | Mon, 15 Nov 2010 10:47:46 -0500 |
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On Mon, 2010-11-15 at 11:32 +0100, Patrick McHardy wrote: > On 13.11.2010 00:14, Hua Zhong wrote: > >> On 11.11.2010 22:58, Hua Zhong wrote: > >>>> 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. > >>> > >>> I would argue that -j DROP should behave exactly as the packet is > >> dropped in the network, while -j REJECT should signal the failure to > >> the application as soon as possible (which it doesn't seem to do). > >> > >> It sends an ICMP error or TCP reset. Interpretation is up to TCP. > > > > Huh? It's the OUTPUT chain we are talking about. There is no ICMP error or > > TCP reset. > > Of course there is. > > ICMP (default): > > iptables -A OUTPUT -p tcp -j REJECT > > TCP reset: > > iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset > > The second one will cause a hard error for the connection.
Well I'm (I guess?) surprised that the --reject-with icmp doesn't do anything with a local outgoing connection but --reject-with tcp-reset does something like what I'm looking for.
I notice the heavy lifting for this is done in net/ipv4/netfilter/ipt_REJECT.c::send_rest() (and something very similar for IPv6)
I really don't want to duplicate that code into SELinux (for obvious reasons) and I'm wondering if anyone has objections to me making it available outside of netlink and/or suggestions on how to make that code available outside of netfilter (aka what header to expose it, and does it still make logical sense in ipt_REJECT.c or somewhere else?)
-Eric
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