bgpd: Set correct TTL for the dynamic neighbor peers #15121
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ton31337
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Jan 9, 2024
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In an EBGP multihop configuration with dynamic neighbors, the TTL configured is not being updated for the socket.
Issue:
Assume the following topology:
Host (Dynamic peer to spine - 192.168.1.100) - Leaf - Spine (192.168.1.1)
When the host establishes a BGP multihop session to the spine,
the connection uses the MAXTTL value instead of the configured TTL (in this case, 2).
This issue is only observed with dynamic peers.
Logs: look at the TTL is still MAXTTL, instead of “2” configured.
18:13:18.872395 48:b0:2d:0c:58:0b > 48:b0:2d:66:64:6b, ethertype IPv4 (0x0800), length 85: (tos 0xc0, ttl 255, id 32078, offset 0, flags [DF], proto TCP (6), length 71)
192.168.1.100.179 > 192.168.1.1.40967: Flags [P.], cksum 0xfe89 (correct), seq 28406:28425, ack 28424, win 255, options [nop,nop,TS val 4192664793 ecr 2814447051], length 19: BGP
Keepalive Message (4), length: 19
Fix:
Whenever a dynamic peer is created, the socket TTL should be updated with the configured TTL, in this case 2.
19:13:24.894890 48:b0:2d:0c:58:0b > 48:b0:2d:66:64:6b, ethertype IPv4 (0x0800), length 85: (tos 0xc0, ttl 2, id 1131, offset 0, flags [DF], proto TCP (6), length 71)
192.168.1.100.179 > 192.168.1.1.41937: Flags [P.], cksum 0x7a67 (correct), seq 2046150759:2046150778, ack 4286110599, win 255, options [nop,nop,TS val 4196270815 ecr 2818051226], length 19: BGP
Keepalive Message (4), length: 19
Testing: UT
UT logs:
2023-12-29T19:13:21.892205+00:00 host bgpd[1591425]: [WWPV7-YSZB5] Dynamic Neighbor 192.168.1.1/32 matches group test listen range 192.168.1.0/30
2023-12-29T19:13:21.892654+00:00 host bgpd[1591425]: [GBPAR-M31QF] 192.168.1.1 Dynamic Neighbor added, group test count 1
2023-12-29T19:13:21.892993+00:00 host bgpd[1591425]: [GPE2H-K9QRE] bgp_set_socket_ttl: set TxTTL on peer (rtrid 0.0.0.0) socket, err = 2, peer ttl 2
Conflicts:
bgpd/bgp_network.c
Ticket: #
Signed-off-by: Rajesh Varatharaj <[email protected]>
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Jan 12, 2024
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@Mergifyio backport stable/9.1 stable/9.0 |
✅ Backports have been created
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This was referenced Jan 12, 2024
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In an EBGP multihop configuration with dynamic neighbors, the TTL configured is not being updated for the socket.
Issue:
Assume the following topology:
Host (Dynamic peer to spine - 192.168.1.100) - Leaf - Spine (192.168.1.1)
When the host establishes a BGP multihop session to the spine, the connection uses the MAXTTL value instead of the configured TTL (in this case, 2). This issue is only observed with dynamic peers.
Logs: look at the TTL is still MAXTTL, instead of “2” configured.
18:13:18.872395 48:b0:2d:0c:58:0b > 48:b0:2d:66:64:6b, ethertype IPv4 (0x0800), length 85: (tos 0xc0, ttl 255, id 32078, offset 0, flags [DF], proto TCP (6), length 71)
192.168.1.100.179 > 192.168.1.1.40967: Flags [P.], cksum 0xfe89 (correct), seq 28406:28425, ack 28424, win 255, options [nop,nop,TS val 4192664793 ecr 2814447051], length 19: BGP
Keepalive Message (4), length: 19
Fix:
Whenever a dynamic peer is created, the socket TTL should be updated with the configured TTL, in this case 2.
19:13:24.894890 48:b0:2d:0c:58:0b > 48:b0:2d:66:64:6b, ethertype IPv4 (0x0800), length 85: (tos 0xc0, ttl 2, id 1131, offset 0, flags [DF], proto TCP (6), length 71)
192.168.1.100.179 > 192.168.1.1.41937: Flags [P.], cksum 0x7a67 (correct), seq 2046150759:2046150778, ack 4286110599, win 255, options [nop,nop,TS val 4196270815 ecr 2818051226], length 19: BGP
Keepalive Message (4), length: 19
Testing: UT
UT logs:
2023-12-29T19:13:21.892205+00:00 host bgpd[1591425]: [WWPV7-YSZB5] Dynamic Neighbor 192.168.1.1/32 matches group test listen range 192.168.1.0/30 2023-12-29T19:13:21.892654+00:00 host bgpd[1591425]: [GBPAR-M31QF] 192.168.1.1 Dynamic Neighbor added, group test count 1 2023-12-29T19:13:21.892993+00:00 host bgpd[1591425]: [GPE2H-K9QRE] bgp_set_socket_ttl: set TxTTL on peer (rtrid 0.0.0.0) socket, err = 2, peer ttl 2
Conflicts:
bgpd/bgp_network.c
Ticket: #
Signed-off-by: Rajesh Varatharaj [email protected]