May 2021 - Bird-users - Mailing Lists

logging via udp
by Alexander Zubkov 13 Dec '23

13 Dec '23

Hello, Made some dirty patch for myself to allow bird to send logs via udp. But it may be useful not only for me, so posting it here. It could be useful when server experiencing high IO-load. As syslog and file operations in bird are blocking, it can be blocked on writing to it for indefinite time, which could lead to various problems like protocol timeouts. So udp logging comes in handy here. The tradeoff is that we can miss some logs if they are not processed in time. You can specify udp log destination like that: log udp [host IP|"hostname"] [port NUMBER|"portname"] ... By default it uses destination ip 127.0.0.1 and port 514. There are some constraints like not much error handling. And this destination replaces file destination, i.e. you can not use those simultaneously and it may leak descriptors and some memory probably if both are specified. It also makes a new socket every time configuration is reloaded even if there is no change in options, but this is not a great deal.

2 9

BIRD show bgp summary for cli
by Roman Bulakh 14 Jun '23

14 Jun '23

Hi, we use BIRD in our environment, and it would be very nice to have some command like `show bgp summary` in juniper. This command show information about peer IP, peer AS, last update, prefixes received/best/exported and last state. Example: bird> show bgp summary Peer AS Last state change Prfx rcvd/best/export State X.X.X.X asXXXX 2021-01-27 6786/6785/109000 Established Y.Y.Y.Y asYYYY 2020-12-16 0/0/0 Passive BGP Error: Hold timer expired The are patch created for BIRD 1.3.4 and 1.3.6, but it would be good to have this in upstream software, without rebuilding and patching. as I understand it, no functionality should be affected by these changes, this is only a visual update for cli. Old patches describes at pages: https://marc.info/?l=bird-users&m=132155489919052&w=2 http://trubka.network.cz/pipermail/bird-users/attachments/20120228/a1499be7… https://bird-users.network.narkive.com/Px6EH3yl/bird-1-3-6-show-bgp-summary…

4 3

Adding more then one bgp community at once
by Борис Коваленко 05 May '23

05 May '23

Hello! Is this possible to add many communites at once? bgp_community.add([(1,1), (1,2)]) is wrong "Setting clist attribute to non-clist value" Regards, Boris -- С уважением, Борис Коваленко

4 5

[PATCH] feature to keep protocol's state while configuring
by Alexander Zubkov 29 Jan '23

29 Jan '23

Hello. I have created a patch (attached) with new protocol option: disabled keep on|off. To keep the protocol's state while loading new config. It is useful when protocols disabled manually in the runtime, but we want to keep that state when loading new config. Patch is attached. I have made it against the current int-new branch.

3 16

IGP Metric to MED
by Corban Johnson 29 Apr '22

29 Apr '22

Hello, I am trying to set MED on a BGP route using the metric value from OSPF, but the attributes of the next-hop route do not seem to be available in filter evolution. Am I missing something? Example Bird 2.0 config: protocol bgp test_peer { bfd on; med metric on; graceful restart on; ipv4 { table test_table; gateway recursive; }; local as 65656; } protocol ospf t1_igp { ipv4 { table test_table; }; } OSPF is distributing loopbacks and link nets only. BGP protocols from ‘test_peer’ will use routes learned from ‘t1_igp’ in ‘test_table’ to resolve next hop information (gateway recursive). So far, so good. However, I also have an eBGP peer (i.e. who is not participating in my IGP above) who is multi homed with AS65656. I would like to use MED to inform the peer about my IGP distances to each exit — something like the ‘metric-out minimum-igp <offset>’ command in Junos (https://www.juniper.net/documentation/en_US/junos/topics/reference/configur…) > You can increase or decrease the variable metric calculated from the IGP metric (either from the igp or minimum-igp statement) by specifying a value for offset. The metric is increased by specifying a positive value for offset, and decreased by specifying a negative value for offset. The problem seems to be that filters may only access attributes of the route currently processed, and the 'gateway recursive’ channel directive only calculates next-hop without passing any route attributes of that next-hop through. Has anyone had any luck trying something similar? Many thanks.

3 5

Re: BIRD trying to reinsert existing kernel routes, netlink issue?
by Zhaofeng Li 18 Feb '22

18 Feb '22

I know this was an old thread, but would really appreciate if anyone is interested in digging in deeper. I can confirm the exact same behavior happens to me on NixOS with the 5.4.69 kernel but not on 4.19.149. BIRD 2.0.7 on 5.4.69 would incessantly attempt to insert the same routes, rendering birdc unusable as it was presumably taking up so much time in the main loop (it was receiving an IPv4 full table over iBGP as well). While it was doing that, it stopped announcing the prefixes of stub interfaces to OSPF neighbors. Thanks, Zhaofeng Li On Sun, Aug 2, 2020, at 17:36 PM, Sasha Romijn wrote: > Hello, > I’m running into a rather complex issue where BIRD tries to reinsert routes into the kernel routing table that are already in there. I’m at the point of suspecting a netlink bug in the 5.x linux kernel. However, I may be entirely off, and would like to hear what people with more BIRD and/or netlink expertise think about it. > My setup is bird 2.0.7 on Ubuntu 20.04. I’ve been able to reproduce this with the default 5.4.0-42-generic kernel as well as the ubuntu mainline 5.7.0-050700-generic kernel. This bird instance has an IBGP peering with another bird 2.0.7 instance, which sends an IPv4 full table. The IBGP peering is set up over a GRE tunnel. There is no other routing software running. I am seeing this issue on another server too, ubuntu 20.04 with 5.4.0-42-generic. A third one with ubuntu 18.04 and a 4.15.0-20-generic kernel, is fine.

3 2

BGP strict bind socket error
by Ben Tremblay 09 Jan '22

09 Jan '22

Hi all, I have encountered a problem with how BIRD opens the listening socket for strict bind BGP. In particular, BIRD sometimes tries to open the listening socket for the protocol when the configured local IP is not yet present on the interface. It seems that BIRD will try to bind the BGP socket to the configured IP if any address exists on the protocol interface that can be used to reach the neighbor. Let me give an example to clarify. I have a minimal reproducible example with the following BGP configuration: router id 192.168.0.1; protocol device { scan time 10; } protocol bgp bgp_01 { ipv4 { import all; export all; }; debug all; local 192.168.0.1 port 179 as 1; neighbor 192.168.0.2 port 179 as 1; interface "host1"; direct; strict bind yes; } Given this configuration, I can reproduce the problem behaviour by starting the protocol with no addressing on the host1 interface and then adding an address which includes the neighbor IP in its subnet, e.g. 192.168.0.3/24. Once this address/route is added, BIRD logs the following: Jan 07 12:09:31 router03 bird[57497]: bgp_01: Neighbor ready Jan 07 12:09:31 router03 bird[57497]: bgp_01: Socket error: bind: Cannot assign requested address Jan 07 12:09:31 router03 bird[57497]: bgp_01: Cannot open listening socket And the protocol enters an error state: BIRD 2.0.6 ready. Name Proto Table State Since Info device1 Device --- up 11:55:51.049 bgp_01 BGP --- down 12:09:31.264 Error: No listening socket The reason this error is so problematic for me is that the protocol cannot recover from this state without administrative intervention (e.g. configuring bird or restarting the protocol). So, I have two questions: 1. Is this correct behaviour? 2. Can I configure BIRD so that my protocol is able to recover after suffering a socket error like this? I should also mention I can actually observe this socket error occur when adding the 'correct' address to the protocol interface, but only in the context of a larger application and only some of the time. Thanks, Ben

4 12

[BIRD 2.0.x] Netlink: ignore dead routes
by Vincent Bernat 09 Jan '22

09 Jan '22

With net.ipv4.conf.XXX.ignore_routes_with_linkdown sysctl, a user can ensure the kernel does not use a route whose target interface is down. The route is marked with a "dead"/RTNH_F_DEAD flag. Currently, BIRD still uses and distributes this route. This patch just ignores such a route. This patch could be backported to 1.6.x. Signed-off-by: Vincent Bernat <vincent(a)bernat.ch> --- sysdep/linux/netlink.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/sysdep/linux/netlink.c b/sysdep/linux/netlink.c index f85bcf35685b..c28126510e6e 100644 --- a/sysdep/linux/netlink.c +++ b/sysdep/linux/netlink.c @@ -1690,6 +1690,9 @@ nl_parse_route(struct nl_parse_state *s, struct nlmsghdr *h) if (i->rtm_flags & RTNH_F_ONLINK) ra->nh.flags |= RNF_ONLINK; + if (i->rtm_flags & RTNH_F_DEAD) + return; + neighbor *nbr; nbr = neigh_find(&p->p, ra->nh.gw, ra->nh.iface, (ra->nh.flags & RNF_ONLINK) ? NEF_ONLINK : 0); -- 2.28.0

5 15

Possibility to treat /32 and /128 non-gateway routes as onlink on BSD?
by Stefan Haller 27 Dec '21

27 Dec '21

Hi everyone, In a recent change in the FreeBSD Wireguard kernel module the POINTTOPOINT interface flag is dropped for wg interfaces[1]. This behaviour will probably not change, because Wireguard is not peer-to-peer or a broadcast domain, but peer-to-multipoint. Hence my previous configuration of setting peer addresses on the interface is not working anymore: ifconfig wg0 inet 192.168.0.10/32 192.168.0.4 The above syntax is for POINTTOPOINT interfaces. In this case 192.168.0.10 is the local address of the interface and 192.168.0.4 is the address of the remote peer. So if one does not want to add a dedicated subnet to every tunnel device, one has to add static host routes similar to these ones: ifconfig wg0 192.168.0.10/32 route add 192.168.0.4 -iface wg0 Note that this actually models the real world better, because Wireguard is not point-to-point but point-to-multipoint. So multiple peers can be done in the following way: ifconfig wg0 192.168.0.10/32 route add 192.168.0.4 -iface wg0 route add 192.168.0.8 -iface wg0 However, this does not work with bird 2.0.8: bird will not recognize the p2p peer addresses as gateways and it will log on kernel table rescan: KRT: Received route 192.168.42.0/24 with strange next-hop 192.168.0.4 KRT: Error sending route 192.168.42.0/24 to kernel: File exists I did have a look why this is happening: bird discards the route, because the gateway does not belong to any of its interface's addresses (the peer address is configured as a static host route and not on the interface). At the same time it forgets that it was bird itself who added the route (because the route is discarded on kernel table rescan, it thinks it is absent in the kernel table but present in bird's internal routing table -> "add" logic triggers) and tries to add the route again (instead of replacing/keeping the route). This explains the cascade of error messages above. While the Linux netlink code allows to handle onlink routes, this functionality is absent in the BSD code path. Unfortunately, on BSD there is no dedicated flag to mark routes as being directly connected onlink routes. On Linux one could add an onlink route like so: ip route add 192.168.0.4 via 192.168.0.4 dev wg0 onlink The command looks quite odd, but it is working. The via clause is necessary in conjunction with onlink. Afterwards a `birdc dump neighbors` verifies that the peer is recognized: 000055db793035c0 192.168.0.4 wg0 wg0 kernel1 000000000000000000000000 scope univ ONLINK (Also the "strange next-hop" message will go away.) I created a patch that emulates the behaviour on FreeBSD. In this patch the onlink setting is heuristically determined by inspecting the RTF_GATEWAY flag (which must be absent) and checking for a /32 or /128 prefix length. I do not see how to handle cases where the destination is a subnet. The patch was tested on FreeBSD 13.0-RELEASE and 14.0-CURRENT. During rescan of the kernel table the above route is now not dropped because the gateway is recognized to be onlink. While in the Linux route the gateway is still set, on FreeBSD it is unset (~RTF_GATEWAY). So I actually use the destination address of the route, because that's the address of the peer. While I tested the functionality on my machines and also checked the output of `birdc dump neighbors`, the patch might be faulty. Please be kind with me and treat it more as a proof of concept. As I am not experienced with bird's code base I do not fully understand how the neighbor cache is working in detail, so the suggested patch might have unexpected side effects. I would appreciate feedback. In case you think the whole idea is not sensible, I would also love to hear suggestions how to get the above setup working. Kind regards, Stefan [1]: https://git.zx2c4.com/wireguard-freebsd/commit/?id=8801509656e955c27ebf4b9b… sysdep/bsd/krt-sock.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/sysdep/bsd/krt-sock.c b/sysdep/bsd/krt-sock.c index ea0cc4d9..4a0f3a7a 100644 --- a/sysdep/bsd/krt-sock.c +++ b/sysdep/bsd/krt-sock.c @@ -547,6 +547,12 @@ krt_read_route(struct ks_msg *msg, struct krt_proto *p, int scan) net->n.addr, a.nh.gw); return; } + } else if ((!ipv6 && pxlen == 32) || (ipv6 && pxlen == 128)) { + /* Treat non gateway /32 and /128 routes as onlink routes and inject this + information into neighbor cache. */ + if (!neigh_find(&p->p, idst, a.nh.iface, NEF_ONLINK)) + log(L_ERR, "KRT: Failed to inject onlink neighbor %I for interface %s", + idst, a.nh.iface->name); } done: -- 2.31.1

2 5

bgp_large_community wildcard in conditional
by Brooks Swinnerton 18 Oct '21

18 Oct '21

Hello, I was wondering if it's possible to create a conditional that matches on a wildcard for a part of a BGP large community. For example: if ([*, 600, 6939]) ~ bgp_large_community then reject; This currently results in a syntax error at the position of the comma after the *.

5 7