[v1.15] Backport FQDN: fix incorrect reaping of newly-expired IPs #31318
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[ upstream commit 03f8c85 ] The FQDN GC subsystem waits before a successful CT GC run before marking IPs as stale. However, we were erroneously marking CT GC as successful even on failure, or when only run for a single family. So, only mark notify FQDN when we've done a successful GC pass for all configured families. Signed-off-by: Casey Callendrello <cdc@isovalent.com>
[ upstream commit b284170 ] A bug was found where a low-TTL name was incorrectly reaped despite being part of an active connection. After looking at logs, and reproducing locally, it was determined that there is an unfortunate interleaving between the DNS and CT GC loops. The code attempts to prevent this issue by ensuring that names inserted after CT GC has started are exempt from reaping. However, we don't actually track the insertion time, we track the DNS TTL expiration time, which is strictly in the past. In fact, it can be up to a minute in the past. We shouldn't rely on timestamps anyways, as the scheduler can always play tricks on us. So, if a CT GC run has started and finished in the time between name expiration and insertion in to zombies, the IP address is immediately considered dead and unnecessarily reaped. Timeline: T1. name expires T2. CT GC starts and finishes T3. Zombies.SetCTGCTime(T2) T4. Zombies.Upsert(name, T1) T5. Zombies.GC() At T5, zombies.GC will remove IPs associated with name, because T2 > T1. The solution is to use an explicit serial number to ensure that CTGC has completed a full run before we are allowed to delete an IP. We actually need to let CT GC run twice, as it may have started before this zombie was added and thus not marked it alive. Additionally, we already have a grace period, the idle connection timeout, that gives applications a chance to re-use an expired IP. However, we did not respect this grace period if the IP in question did not have an entry in conntrack. So, pad deletion time by this grace period as well, just to be sure this grace period applies to all possible deletions. Signed-off-by: Casey Callendrello <cdc@isovalent.com>
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