ipv6: Dump route exceptions if requested
Since commit 2b760fcf ("ipv6: hook up exception table to store dst cache"), route exceptions reside in a separate hash table, and won't be found by walking the FIB, so they won't be dumped to userspace on a RTM_GETROUTE message. This causes 'ip -6 route list cache' and 'ip -6 route flush cache' to have no function anymore: # ip -6 route get fc00:3::1 fc00:3::1 via fc00:1::2 dev veth_A-R1 src fc00:1::1 metric 1024 expires 539sec mtu 1400 pref medium # ip -6 route get fc00:4::1 fc00:4::1 via fc00:2::2 dev veth_A-R2 src fc00:2::1 metric 1024 expires 536sec mtu 1500 pref medium # ip -6 route list cache # ip -6 route flush cache # ip -6 route get fc00:3::1 fc00:3::1 via fc00:1::2 dev veth_A-R1 src fc00:1::1 metric 1024 expires 520sec mtu 1400 pref medium # ip -6 route get fc00:4::1 fc00:4::1 via fc00:2::2 dev veth_A-R2 src fc00:2::1 metric 1024 expires 519sec mtu 1500 pref medium because iproute2 lists cached routes using RTM_GETROUTE, and flushes them by listing all the routes, and deleting them with RTM_DELROUTE one by one. If cached routes are requested using the RTM_F_CLONED flag together with strict checking, or if no strict checking is requested (and hence we can't consistently apply filters), look up exceptions in the hash table associated with the current fib6_info in rt6_dump_route(), and, if present and not expired, add them to the dump. We might be unable to dump all the entries for a given node in a single message, so keep track of how many entries were handled for the current node in fib6_walker, and skip that amount in case we start from the same partially dumped node. When a partial dump restarts, as the starting node might change when 'sernum' changes, we have no guarantee that we need to skip the same amount of in-node entries. Therefore, we need two counters, and we need to zero the in-node counter if the node from which the dump is resumed differs. Note that, with the current version of iproute2, this only fixes the 'ip -6 route list cache': on a flush command, iproute2 doesn't pass RTM_F_CLONED and, due to this inconsistency, 'ip -6 route flush cache' is still unable to fetch the routes to be flushed. This will be addressed in a patch for iproute2. To flush cached routes, a procfs entry could be introduced instead: that's how it works for IPv4. We already have a rt6_flush_exception() function ready to be wired to it. However, this would not solve the issue for listing. Versions of iproute2 and kernel tested: iproute2 kernel 4.14.0 4.15.0 4.19.0 5.0.0 5.1.0 5.1.0, patched 3.18 list + + + + + + flush + + + + + + 4.4 list + + + + + + flush + + + + + + 4.9 list + + + + + + flush + + + + + + 4.14 list + + + + + + flush + + + + + + 4.15 list flush 4.19 list flush 5.0 list flush 5.1 list flush with list + + + + + + fix flush + + + + v7: - Explain usage of "skip" counters in commit message (suggested by David Ahern) v6: - Rebase onto net-next, use recently introduced nexthop walker - Make rt6_nh_dump_exceptions() a separate function (suggested by David Ahern) v5: - Use dump_routes and dump_exceptions from filter, ignore NLM_F_MATCH, update test results (flushing works with iproute2 < 5.0.0 now) v4: - Split NLM_F_MATCH and strict check handling in separate patches - Filter routes using RTM_F_CLONED: if it's not set, only return non-cached routes, and if it's set, only return cached routes: change requested by David Ahern and Martin Lau. This implies that iproute2 needs a separate patch to be able to flush IPv6 cached routes. This is not ideal because we can't fix the breakage caused by 2b760fcf entirely in kernel. However, two years have passed since then, and this makes it more tolerable v3: - More descriptive comment about expired exceptions in rt6_dump_route() - Swap return values of rt6_dump_route() (suggested by Martin Lau) - Don't zero skip_in_node in case we don't dump anything in a given pass (also suggested by Martin Lau) - Remove check on RTM_F_CLONED altogether: in the current UAPI semantic, it's just a flag to indicate the route was cloned, not to filter on routes v2: Add tracking of number of entries to be skipped in current node after a partial dump. As we restart from the same node, if not all the exceptions for a given node fit in a single message, the dump will not terminate, as suggested by Martin Lau. This is a concrete possibility, setting up a big number of exceptions for the same route actually causes the issue, suggested by David Ahern. Reported-by:Jianlin Shi <jishi@redhat.com> Fixes: 2b760fcf ("ipv6: hook up exception table to store dst cache") Signed-off-by:
Stefano Brivio <sbrivio@redhat.com> Reviewed-by:
David Ahern <dsahern@gmail.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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