App crashes on launch (SIGSYS, futex_time64) on 32-bit Android 8–10 since v0.6.0-rc.4 — CI builds with Go 1.26.0 instead of the go.mod toolchain (go1.26.7)

[ghhv]

Before posting

• I searched existing discussions and issues, including closed ones, and checked the relevant docs.
• I believe this is a product bug rather than a configuration or setup question.
• I can reproduce this issue, or for intermittent issues I've included trigger, frequency, and timing details below.
• I removed or anonymized sensitive data from logs, screenshots, and configuration.

Affected area

Client / Agent

Deployment type

NetBird Cloud

Operating system or environment

Android

NetBird version and upgrade status

client - . v0.6.0 and v0.6.1 (core v0.78.0+)

Did this work before?

Yes, this worked before

Regression details

Affected: v0.6.0-rc.4 onwards, incl. v0.6.0 and v0.6.1 (core v0.78.0+)

• Last working stable: v0.5.0 (core v0.71.0, Go 1.25)

Summary

Since the core bump to Go 1.26 (netbird v0.78.0, commit 12e8874), the Android app crashes about one second after launch on 32-bit ARM devices running Android 8.0–10. Every launch dies with a seccomp SIGSYS on futex_time64. v0.6.0 and v0.6.1 are affected, from both Play and the GitHub release APK.

Current behavior

crashes on start-up - see below

Expected behavior

not crash

Steps to reproduce

install, open

Environment and topology

see below

Self-hosted details, if available

No response

Logs, status output, or debug evidence

### Environment
- Device: N60 rugged scanner (MediaTek), Android 10 (`N60/N60/N60:10/QP1A.190711.020`)
- ABI: armeabi-v7a (32-bit)
- Kernel: `4.9.188`
- Affected: v0.6.0-rc.4 onwards, incl. v0.6.0 and v0.6.1 (core v0.78.0+)
- Last working stable: v0.5.0 (core v0.71.0, Go 1.25)

### Crash (tombstone, v0.6.1 sideloaded from GitHub releases)
    F libc    : Fatal signal 31 (SIGSYS), code 1 (SYS_SECCOMP) in tid 6144 (.netbird.client)
    F DEBUG   : ABI: 'arm'
    F DEBUG   : Cause: seccomp prevented call to disallowed arm system call 422
    F DEBUG   :     r1 00000081 ... r7 000001a6
    F DEBUG   : backtrace:
    F DEBUG   :       #00 pc 000b25d0  /data/app/io.netbird.client-.../base.apk
    I Zygote  : Process 6089 exited due to signal 31 (Bad system call)

Syscall 422 on 32-bit ARM is `futex_time64` (r7 = 0x1a6); r1 = 0x81 is FUTEX_WAKE_PRIVATE from the Go runtime. Android 8.0–10 doesn't allowlist this syscall for apps, and the seccomp filter kills the process instead of returning ENOSYS.

### Root cause
- Go 1.26.0 started calling `futex_time64` first on 32-bit Linux and falling back on ENOSYS: golang/go#77621.
- Go fixed this in **1.26.5**. The runtime now chooses 64-bit time syscalls from the kernel version (≥ 5.1) instead of probing.
- `netbird/go.mod` has `go 1.26.0` / `toolchain go1.26.7`, which would include the fix.
- But `.github/actions/build-android/action.yml` uses `actions/setup-go@v5` with `go-version-file: "netbird/go.mod"`. setup-go v5 only parses the `go` directive (`^go (\d+...)`) and ignores `toolchain`, so CI installs Go **1.26.0**.
- Confirmed from the released v0.6.1 APK: `lib/armeabi-v7a/libgojni.so` embeds **`go1.26.0`**.

### Suggested fix
- Pin the Go version explicitly in the build action (e.g. `go-version: "1.26.8"`), or use a setup-go version that honours the `toolchain` directive.
- Optionally, add a CI check that the Go version embedded in `libgojni.so` matches the intended toolchain.

### Workaround
Install v0.5.0 (or v0.6.0-rc.3, the last build on Go 1.25) from GitHub releases and disable auto-update.

Related issues or discussions

seems same netbirdio/android-client#272

Impact

No response

Additional context

resolution suggestion from Claude

[nakulmanimala]

Also affects v0.6.2: libgojni.so in the v0.6.2 release APK is built with go1.26.0, and it crashes the same way on a Xiaomi Mi TV (Android 10, armeabi-v7a).

Two details for the fix: the kernel-version check landed in Go 1.26.3, and pinning Go only in the CI action is not enough for local builds, because gomobile bind builds in a temporary module that drops the toolchain directive.

PR: netbirdio/android-client#292