bgpd: fix ipv6 nexthop-local unchanged #17037
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cunningr
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Oct 8, 2024
This reverts commit 5f6a61f. Signed-off-by: Louis Scalbert <[email protected]>
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ton31337
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Do not add an IPv6 link-local nexthop if the originating peer does not provide one and the nexthop-local unchanged setting is enabled. Signed-off-by: Louis Scalbert <[email protected]>
If the "nexthop-local unchanged" setting is enabled, it preserves the IPv6 link-local nexthop from the originating peer. However, if the originating and destination peers are not on the same network segment, the originating peer's IPv6 link-local address will be unreachable from the destination peer. In such cases, reset the IPv6 link-local nexthop, even if "nexthop-local unchanged" is set on the destination peer. Signed-off-by: Louis Scalbert <[email protected]>
Add bgp_nexthop_ipv6 to check the ipv6 link-local nexthop conformity in several situations. Signed-off-by: Louis Scalbert <[email protected]>
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@Mergifyio backport dev/10.2 |
✅ Backports have been created
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AS 65000 | AS 65001
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RR |
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R1 --- | --- R2
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When r1 peer is an iBGP route reflector client of rr and r2 peer is a
eBGP neighbor of rr, and all three routers shares the same network, r2
receives announcements coming from r1 with a IPv6 link-local nexthop
from rr. This is incorrect as r2 should send traffic to r1 without
involving rr.
Do not send an IPv6 link-local nexthop if the originating peer is a
route-reflector client.
Link: FRRouting#16219 (comment)
Link: FRRouting#17037 (comment)
Signed-off-by: Louis Scalbert <[email protected]>
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bgpd: fix ipv6 nexthop-local unchanged (backport #17037)
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AS 65000 | AS 65001
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RR |
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R1 --- | --- R2
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When r1 peer is an iBGP route reflector client of rr and r2 peer is a
eBGP neighbor of rr, and all three routers shares the same network, r2
receives announcements coming from r1 with a IPv6 link-local nexthop
from rr. This is incorrect as r2 should send traffic to r1 without
involving rr.
Do not send an IPv6 link-local nexthop if the originating peer is a
route-reflector client.
Link: FRRouting#16219 (comment)
Link: FRRouting#17037 (comment)
Signed-off-by: Louis Scalbert <[email protected]>
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#16219 attempted to solve #16198 issue but removed ipv6 link-local nexthop in situation it was legitimate. For example, when an ipv4-mapped IPv6 address is present in global IPv6 nexthop, the link-local is also useful if the peer does not understand the ipv4-mapped IPv6 address format.
Revert #16219 and apply fixes to the "ipv6 nexthop-local unchanged" behavior. When the parameter is present:
Add a topotest to check the ipv6 nexthops in various situations including the use case from #16219 (comment) and #17037 (comment)