channeld: do not enforce max_accepted_htlcs on LOCAL in channel reinit #5640
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If a channel goes offline while the count of outstanding outgoing HTLCs exceeds the limit that we enforce against the peer, then the channel could never be brought online again because `add_htlc` called by `channel_force_htlcs` in `channeld/full_channel.c` would return `CHANNEL_ERR_TOO_MANY_HTLCS`. The protocol specification actually does allow us to exceed the limits that we are enforcing against the peer; we are only prohibited from exceeding the limits that the peer is enforcing against us. `add_htlc` takes an `enforce_aggregate_limits` parameter that appears to have been intended for `channel_force_htlcs` to exempt the local node from obeying the limits that it is enforcing against the peer, but this parameter was only being respected for the total HTLC value-in-flight check but not for the HTLC count check. This commit respects the parameter for the HTLC count check as well and resolves the problem of "Could not restore HTLCs". Fixes: ElementsProject#5636 Changelog-Fixed: channeld: Channel reinitialization no longer fails when the number of outstanding outgoing HTLCs exceeds `max_accepted_htlcs`.
cdecker
approved these changes
Sep 28, 2022
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If a channel goes offline while the count of outstanding outgoing HTLCs exceeds the limit that we enforce against the peer, then the channel could never be brought online again because
add_htlccalled bychannel_force_htlcsinchanneld/full_channel.cwould returnCHANNEL_ERR_TOO_MANY_HTLCS. The protocol specification actually does allow us to exceed the limits that we are enforcing against the peer; we are only prohibited from exceeding the limits that the peer is enforcing against us.add_htlctakes anenforce_aggregate_limitsparameter that appears to have been intended forchannel_force_htlcsto exempt the local node from obeying the limits that it is enforcing against the peer, but this parameter was only being respected for the total HTLC value-in-flight check but not for the HTLC count check. This commit respects the parameter for the HTLC count check as well and resolves the problem of "Could not restore HTLCs".Fixes: #5636
Changelog-Fixed: channeld: Channel reinitialization no longer fails when the number of outstanding outgoing HTLCs exceeds
max_accepted_htlcs.