iBGP stuck in connect state

[Alexander Zubkov]

Not always, sometimes it is rp_filter to be blamed. :)
On Fri, Dec 7, 2018 at 12:40 AM Brooks Swinnerton <bswinnerton at gmail.com> wrote:
>
> Ah ha, it was the firewall. It's always the firewall.
>
> On Wed, Dec 5, 2018 at 11:51 PM Brooks Swinnerton <bswinnerton at gmail.com> wrote:
>>
>> Hello,
>>
>> I'm having trouble configuring two BIRD instances to talk to one another over a wireguard tunnel with iBGP. They both stay in a `Connect` state.
>>
>> With debug <protocol> all, I only see:
>>
>> ```
>> Dec 05 23:31:32 border bird[3460]: foo: Connecting to 169.254.2.2 from local address 169.254.3.3
>> Dec 05 23:33:19 border bird[3460]: foo: Connecting to 169.254.2.2 from local address 169.254.3.3
>> Dec 05 23:35:13 border bird[3460]: foo: Connecting to 169.254.2.2 from local address 169.254.3.3
>> ```
>>
>> The wireguard tunnel is up, and each side can ping the other:
>>
>> ```
>> PING 169.254.2.2 (169.254.2.2) 56(84) bytes of data.
>> 64 bytes from 169.254.2.2: icmp_seq=1 ttl=64 time=66.7 ms
>> 64 bytes from 169.254.2.2: icmp_seq=2 ttl=64 time=66.6 ms
>> 64 bytes from 169.254.2.2: icmp_seq=3 ttl=64 time=66.8 ms
>> ```
>>
>> ```
>> PING 169.254.3.3 (169.254.3.3) 56(84) bytes of data.
>> 64 bytes from 169.254.3.3: icmp_seq=1 ttl=64 time=66.5 ms
>> 64 bytes from 169.254.3.3: icmp_seq=2 ttl=64 time=66.2 ms
>> 64 bytes from 169.254.3.3: icmp_seq=3 ttl=64 time=66.3 ms
>> ```
>>
>> I can even see some BGP traffic when doing a tcpdump:
>>
>> ```
>> 23:44:16.487852 ip: (tos 0xc0, ttl 64, id 40780, offset 0, flags [DF], proto TCP (6), length 60)
>>     169.254.3.3.53585 > 169.254.2.2.179: Flags [S], cksum 0x5930 (incorrect -> 0x61e7), seq 4023371188, win 27600, options [mss 1380,sackOK,TS val 891392 ecr
>> 0,nop,wscale 7], length 0
>> 23:44:16.989732 ip: (tos 0xc0, ttl 64, id 29307, offset 0, flags [DF], proto TCP (6), length 60)
>>     169.254.2.2.46081 > 169.254.3.3.179: Flags [S], cksum 0x3ae5 (correct), seq 156366469, win 27600, options [mss 1380,sackOK,TS val 889856 ecr 0,nop,wscale
>> 7], length 0
>> 23:44:18.535863 ip: (class 0xc0, flowlabel 0xe9696, hlim 64, next-header TCP (6) payload length: 40) fd00:169:254:3::3.47019 > fd00:169:254:2::2.179: Flags [S], cksum 0x01b4 (incorrect -> 0x5b17), seq 1562824692, win 27200, options [mss 1360,sackOK,TS val 891904 ecr 0,nop,wscale 7], length 0
>> 23:44:33.117481 ip: (tos 0xc0, ttl 64, id 29308, offset 0, flags [DF], proto TCP (6), length 60)
>>     169.254.2.2.46081 > 169.254.3.3.179: Flags [S], cksum 0x2b25 (correct), seq 156366469, win 27600, options [mss 1380,sackOK,TS val 893888 ecr 0,nop,wscale 7], length 0
>> 23:44:37.610488 ip: (class 0xc0, flowlabel 0xeaf06, hlim 64, next-header TCP (6) payload length: 40) fd00:169:254:2::2.36355 > fd00:169:254:3::3.179: Flags [S], cksum 0x243b (correct), seq 476210459, win 27200, options [mss 1360,sackOK,TS val 895010 ecr 0,nop,wscale 7], length 0
>> 23:44:38.621468 ip: (class 0xc0, flowlabel 0xd3b4f, hlim 64, next-header TCP (6) payload length: 40) fd00:169:254:2::2.36355 > fd00:169:254:3::3.179: Flags [S], cksum 0x233d (correct), seq 476210459, win 27200, options [mss 1360,sackOK,TS val 895264 ecr 0,nop,wscale 7], length 0
>> 23:44:40.637418 ip: (class 0xc0, flowlabel 0xd41b0, hlim 64, next-header TCP (6) payload length: 40) fd00:169:254:2::2.36355 > fd00:169:254:3::3.179: Flags [S], cksum 0x2145 (correct), seq 476210459, win 27200, options [mss 1360,sackOK,TS val 895768 ecr 0,nop,wscale 7], length 0
>> 23:44:44.893305 ip: (class 0xc0, flowlabel 0xcc08e, hlim 64, next-header TCP (6) payload length: 40) fd00:169:254:2::2.36355 > fd00:169:254:3::3.179: Flags [S], cksum 0x1d1d (correct), seq 476210459, win 27200, options [mss 1360,sackOK,TS val 896832 ecr 0,nop,wscale 7], length 0
>> ```
>>
>> The bird.conf file is identical between hosts can be found in: https://gist.github.com/bswinnerton/9ffa236a55f120ba9491658ae74a841a.
>>
>> Does anything seem amiss? What's odd is that I can establish iBGP connections with other BGP routers that are not running BIRD with the exact same iBGP peer configuration.
>>
>> $ sudo birdc -v
>> 0001 BIRD 2.0.2 ready.