fix(socket): SO_REUSEADDR on UDP for post-suspend rebind - #121
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got3nks merged 1 commit intoJun 13, 2026
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After resume from suspend, CMuleUDPSocket::OnReceive's read callback
sometimes delivers an error (or sees !m_socket->IsOk()) and drives a
DestroySocket() + CreateSocket() cycle to recover. The destroy step
closes the previous fd, but on some kernels the binding is still
considered live for a short window, so the immediate rebind in the
new socket hits EADDRINUSE:
Error creating UDP socket 0.0.0.0 4672 : Address already in use
MuleUDPSocket: Failed to create valid Client UDP-Socket
With the rebind failing, Kad never gets a working UDP socket back
("Kad: Connecting" forever) and ed2k client UDP is broken until the
user fully restarts amule.
Set SO_REUSEADDR on the UDP socket between open() and bind() so the
close-then-bind sequence is permitted by the kernel. The TCP acceptor
path already sets reuse_address(true) for the same reason; this just
applies the same option to the UDP path.
Refs amule-org#103.
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Summary
Refs #103. Fixes a Kad / ed2k-client-UDP wedge after suspend/resume on Linux (reported by @demanuel against the Flatpak prerelease).
Root cause
CMuleUDPSocket::OnReceivedrives aDestroySocket()+CreateSocket()self-recovery cycle whenever a read callback returns an error or!IsOk(). On Linux, aftersystemd-suspendreturns, the first post-resume read sometimes delivers a transient error that hits this path. The destroy step closes the previous fd, but the kernel can still consider the binding live for a short window, so the immediate rebind fails:With the rebind failing, Kad never gets a working UDP socket back ("Kad: Connecting" forever) and ed2k client UDP is broken until the user fully restarts amule. demanuel's log +
ss -tan | grep :4661(empty) at #103 ruled out the earlier TCP-stuck-dead hypothesis and pointed straight at the UDP rebind path.Fix
Set
SO_REUSEADDRon the UDP socket betweenopen()andbind()inCAsioUDPSocketImpl::CreateSocket. The TCP acceptor path at LibSocketAsio.cpp:995 already setsreuse_address(true)for the equivalent reason; this is the same fix applied to the UDP path.No behavioural change for the cold-start case — the option only matters when there's a previous binding the kernel hasn't fully released yet.
Status
Draft. Pending real-world confirmation from @demanuel that a suspend/resume cycle no longer wedges Kad. Packaging artifacts will be built from this branch on the fork (
got3nks/amule) so demanuel can download a Flatpak/AppImage/Windows zip without building from source.Test plan