Support OpenWRT and wmediumd snapshot/restore by Elie-Kh · Pull Request #3197 · google/android-cuttlefish

Elie-Kh · 2026-09-17T23:22:53Z

Enable proper snapshot save and restore for OpenWRT AP instances and their vhost-user mac80211_hwsim connections in wmediumd:

Patch external wmediumd to implement vhost-user device state save (SLEEP + GET_VRING_BASE + DEVICE_STATE) and restore (DEVICE_STATE + SET_VRING_ADDR + SET_VRING_BASE + SET_VRING_KICK + SET_VRING_CALL + WAKE) callbacks so existing vhost-user clients can reconnect and resume without losing station/queue state or spinning on stale EPOLLHUP events.
Update CvdBootStateMachine to explicitly resume the OpenWRT crosvm instance (crosvm resume <sock> --full) upon guest restore completion, replacing the previous service network restart LuciRPC workaround.
Check that the OpenWRT snapshot directory exists before passing --restore to crosvm when launching OpenWrt, falling back to a cold boot with a warning if absent.
Cache the discovered OpenWRT IP address in OpenwrtControlServiceImpl so IP lookups continue to succeed after restoring from a snapshot when launcher.log no longer emits fresh boot logs.

Bug: 335361533
Test: Verified snapshot take and restore with OpenWRT Wi-Fi enabled
TAG=agy
CONV=5df97b60-361a-4803-9dc9-6c486b536214

Databean

Added @jemoreira for the wmediumd changes for vhost-user experience

Databean · 2026-09-17T23:32:49Z

+From 4d439a3686758dde1a6707781988f2a4efdd57f3 Mon Sep 17 00:00:00 2001
+From: Elie Kheirallah <khei@google.com>
+Date: Fri, 4 Sep 2026 17:40:12 +0000
+Subject: [PATCH] wmediumd: Implement device state save and restore for
+ snapshot


Is there a plan to send this wmediumd upstream as well? Honestly I'm not sure what the upstream is at this point, https://github.com/ramonfontes/wmediumd looks like it has the most recent changes, but the code imported to Android is based on this version: https://github.com/bcopeland/wmediumd , and that's also what this build_external code references.

It's probably worth investigating deltas. If we aren't too divergent from https://github.com/ramonfontes/wmediumd, it might be worthwhile consolidating.

Databean · 2026-09-17T23:55:25Z

+              }
+            }
+            if (openwrt_restored) {
+              const auto openwrt_sock = instance_.OpenwrtCrosvmSocketPath();


We have WaitForUnixSocket with a ListeningWithoutConnect variation. The difference is one will periodically try to connect, and the other will not.

Databean · 2026-09-18T00:11:12Z

+                  SubprocessOptions(), WEXITED);
+              CHECK(infop.has_value())
+                  << "Failed to execute crosvm resume for OpenWRT: "
+                  << infop.error();
+              CHECK_EQ(infop->si_code, CLD_EXITED);
+              CHECK_EQ(infop->si_status, 0)
+                  << "crosvm resume for OpenWRT returned non-zero code "
+                  << infop->si_status;


This can use the fewer-arguments version of Execute which has comparable behavior and a simpler return type:

android-cuttlefish/base/cvd/cuttlefish/process/execute.cc

Lines 33 to 42 in 01a5427

int Execute(std::vector<std::string> command) {

// NOLINTNEXTLINE(misc-include-cleaner): <sys/wait.h> provides siginfo_t

const Result<siginfo_t> result =

Execute(std::move(command), SubprocessOptions(), WEXITED);

if (result.has_value() && result->si_code == CLD_EXITED) {

return result->si_status; // NOLINT(misc-include-cleaner): <signal.h>

} else {

return -1;

}

}

Enable proper snapshot save and restore for OpenWRT AP instances and their vhost-user mac80211_hwsim connections in wmediumd: - Patch external wmediumd to implement vhost-user device state save (SLEEP + GET_VRING_BASE + DEVICE_STATE) and restore (DEVICE_STATE + SET_VRING_ADDR + SET_VRING_BASE + SET_VRING_KICK + SET_VRING_CALL + WAKE) callbacks so existing vhost-user clients can reconnect and resume without losing station/queue state or spinning on stale EPOLLHUP events. - Update CvdBootStateMachine to explicitly resume the OpenWRT crosvm instance (`crosvm resume <sock> --full`) upon guest restore completion, replacing the previous `service network restart` LuciRPC workaround. - Check that the OpenWRT snapshot directory exists before passing `--restore` to crosvm when launching OpenWrt, falling back to a cold boot with a warning if absent. - Cache the discovered OpenWRT IP address in OpenwrtControlServiceImpl so IP lookups continue to succeed after restoring from a snapshot when launcher.log no longer emits fresh boot logs. Bug: 335361533 Test: Verified snapshot take and restore with OpenWRT Wi-Fi enabled TAG=agy CONV=5df97b60-361a-4803-9dc9-6c486b536214

Databean · 2026-09-18T20:10:28Z

+Subject: [PATCH] wmediumd: Implement device state save and restore for
+ snapshot


It occurs to me also that because we don't have an internal build of wmediumd, this PR might cause problems for Google employees trying to use the internal Cuttlefish host tools build to launch non-git_main devices like AOSP builds because they'll be using the latest run_cvd but an older build of wmediumd.

Good point.. Have we had a precedence of this?

Two similar cases I can think of, neither with a satisfying / relevant conclusion:

secure_env has had additional feature work on git_main, and I'm pushing to get that ported to the github project.

netsim has had additional feature work on git_main. We're trying to temporarily roll back shipping netsim in our debian package until netsim finalizes their own github release that we can rely on.

Elie-Kh requested a review from Databean September 17, 2026 23:22

Databean requested a review from jemoreira September 18, 2026 00:21

Databean approved these changes Sep 18, 2026

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jemoreira approved these changes Sep 18, 2026

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Elie-Kh force-pushed the openwrt-snapres-support branch 5 times, most recently from ef38f2d to 2ce0b5d Compare September 18, 2026 19:41

Elie-Kh force-pushed the openwrt-snapres-support branch from 2ce0b5d to 095d508 Compare September 18, 2026 19:42

Databean reviewed Sep 18, 2026

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Support OpenWRT and wmediumd snapshot/restore - #3197

Support OpenWRT and wmediumd snapshot/restore#3197
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Elie-Kh:openwrt-snapres-support

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	int Execute(std::vector<std::string> command) {
	// NOLINTNEXTLINE(misc-include-cleaner): <sys/wait.h> provides siginfo_t
	const Result<siginfo_t> result =
	Execute(std::move(command), SubprocessOptions(), WEXITED);
	if (result.has_value() && result->si_code == CLD_EXITED) {
	return result->si_status; // NOLINT(misc-include-cleaner): <signal.h>
	} else {
	return -1;
	}
	}

		Subject: [PATCH] wmediumd: Implement device state save and restore for
		snapshot

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