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fix: resolve argv[0] misparse and SIGSEGV hang in JNI bridge

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Two root causes prevented iperf3 tests from running:

1. argv[0] bug: iperf_parse_arguments() expects argv[0] to be the
   program name. We passed Dart args directly, so argv[0] was '-c',
   which iperf3 misinterpreted as the program name → 'Argument parse
   error: must either be a client (-c) or server (-s)'. Fixed by
   prepending "iperf3" as argv[0] and shifting user args to argv[1+].

2. Signal handling: iperf_catch_sigend() installs handlers that use
   longjmp() to a jmp_buf, but we never initialized the buffer with
   setjmp(). Any signal during iperf_run_client() caused SIGSEGV or
   hang. Added setjmp/longjmp wrapper matching main.c's pattern,
   SIGPIPE=SIG_IGN, and a 30s connect_timeout to avoid DNS hangs.

Also extracted iperf_cleanup_and_signal() to deduplicate the
normal-return and longjmp paths. Added diagnostic logging to
IperfRunner.kt's library loading for faster future debugging.
This commit is contained in:
Irene Koivisto
2026-08-26 01:52:37 +09:00
parent 7263808918
commit a31cdef775
2 changed files with 168 additions and 63 deletions
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android/app/src/main/cpp/iperf_jni.c
+160 -62
View File
@@ -4,6 +4,13 @@
* This file exposes iperf3's API to Java/Kotlin via JNI, enabling
* the Flutter app to run iperf3 tests natively inside the app process
* (no Process.start needed, no SELinux restrictions).
*
* SIGNAL HANDLING NOTE:
* iperf3's run() function (called from iperf_run_client()) uses
* setjmp/longjmp for graceful signal handling. The JNI bridge must
* replicate this setup — otherwise iperf_catch_sigend() installs
* handlers that longjmp to an unset buffer, causing undefined
* behaviour (typically a SIGSEGV or hang).
*/
#include <stdio.h>
@@ -11,6 +18,8 @@
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <setjmp.h>
#include <signal.h>
#include <android/log.h>
#include <jni.h>
#include <pthread.h>
@@ -159,6 +168,62 @@ static void free_argv(char **argv, int argc) {
free(argv);
}
/* ------------------------------------------------------------------ */
/* Internal: clean up after iperf_run_client returns (normal path). */
/* Must be called only on the normal return path (NOT after longjmp). */
/* ------------------------------------------------------------------ */
static void iperf_cleanup_and_signal(JNIEnv *env,
struct iperf_run_state *state,
char **argv, int argc,
int ret, int stopped) {
/* Wait for reader thread to finish */
pthread_join(state->reader_thread, NULL);
/* Flush and close output */
fflush(state->outfile);
fclose(state->outfile);
/* Clean up iperf */
iperf_free_test(g_test);
g_test = NULL;
/* Free argv */
free_argv(argv, argc);
/* Signal result to Java */
if (stopped) {
signal_output(state, "[iPerf JNI] Test was stopped by user.\n");
} else if (ret < 0) {
char errbuf[256];
snprintf(errbuf, sizeof(errbuf),
"[iPerf JNI] Test failed: %s\n",
iperf_strerror(i_errno));
signal_error(state, errbuf);
} else {
signal_output(state, "[iPerf JNI] Test completed successfully.\n");
}
/* Signal completion to Java */
signal_complete(state);
/* Free global ref and state struct */
(*env)->DeleteGlobalRef(env, state->callback_ref);
free(state);
}
/* ------------------------------------------------------------------ */
/* Per-call signal handling state. */
/* Must be static so it survives across the longjmp back to setjmp. */
/* ------------------------------------------------------------------ */
static jmp_buf g_sigend_jmp_buf;
static volatile int g_signed_sig = 0;
/* Signal handler — mirrors main.c::sigend_handler */
static void sigend_handler(int sig) {
g_signed_sig = sig;
longjmp(g_sigend_jmp_buf, 1);
}
/* ------------------------------------------------------------------ */
/* JNI: Start an iperf3 test with the given arguments. */
/* Signature: void runIperfLive(String[] args, IperfCallback cb) */
@@ -179,26 +244,47 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
iperf_defaults(test);
g_test = test;
/* Convert Java String[] -> char** argv */
int argc = 0;
char **argv = java_string_array_to_argv(env, arguments, &argc);
/*
* Convert Java String[] -> char** argv, prepending "iperf3" as argv[0].
* iperf_parse_arguments() expects argv[0] to be the program name;
* passing args directly from Dart means argv[0] would be "-c",
* which iperf3 misinterprets as the program name, not the client flag.
*/
int dart_argc = (*env)->GetArrayLength(env, arguments);
int total_argc = dart_argc + 1; /* +1 for "iperf3" */
char **argv = malloc((total_argc + 1) * sizeof(char *));
if (!argv) {
const char *err = "Failed to parse arguments";
signal_error((struct iperf_run_state *) 0, err);
const char *err = "Failed to allocate argv";
LOGE("%s", err);
iperf_free_test(test);
g_test = NULL;
return;
}
argv[0] = strdup("iperf3");
for (int i = 0; i < dart_argc; i++) {
jstring jstr = (jstring) (*env)->GetObjectArrayElement(env, arguments, i);
const char *cstr = (*env)->GetStringUTFChars(env, jstr, NULL);
if (cstr) {
argv[i + 1] = strdup(cstr);
(*env)->ReleaseStringUTFChars(env, jstr, cstr);
} else {
argv[i + 1] = strdup("");
}
(*env)->DeleteLocalRef(env, jstr);
}
argv[total_argc] = NULL; /* NULL-terminated for iperf */
/* Set a reasonable connect timeout (30s) to avoid hanging on DNS resolution.
* Default iperf3 connect timeout is 120s which is far too long. */
test->settings->connect_timeout = 30000;
/* Parse arguments */
if (iperf_parse_arguments(test, argc, argv) < 0) {
if (iperf_parse_arguments(test, total_argc, argv) < 0) {
char errbuf[256];
snprintf(errbuf, sizeof(errbuf), "Argument parse error: %s",
iperf_strerror(i_errno));
free_argv(argv, argc);
signal_error((struct iperf_run_state *) 0, errbuf);
snprintf(errbuf, sizeof(errbuf),
"Argument parse error: %s", iperf_strerror(i_errno));
LOGE("%s", errbuf);
free_argv(argv, total_argc);
iperf_free_test(test);
g_test = NULL;
return;
@@ -207,7 +293,7 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
/* Create a pipe to capture iperf's stdout/stderr */
int pipefd[2];
if (pipe(pipefd) != 0) {
free_argv(argv, argc);
free_argv(argv, total_argc);
const char *err = "Failed to create output pipe";
LOGE("pipe() failed: %s", strerror(errno));
@@ -222,7 +308,7 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
struct iperf_run_state *state =
calloc(1, sizeof(struct iperf_run_state));
if (!state) {
free_argv(argv, argc);
free_argv(argv, total_argc);
close(pipefd[0]);
close(pipefd[1]);
iperf_free_test(test);
@@ -253,60 +339,72 @@ Java_com_novoyuuparosk_iperf3gui_IperfRunner_runIperfLive(
test->outfile = state->outfile;
setvbuf(test->outfile, NULL, _IOLBF, 0); /* Line-buffered */
/* Notify Java that the test is starting */
signal_output(state, "[iPerf JNI] Starting iPerf3 client...\n");
/*
* Set up signal handling BEFORE calling iperf_run_client().
* iperf3's run() function uses setjmp/longjmp for signal handling.
* - setjmp returns 0 on first call (normal path)
* - setjmp returns non-zero when called via longjmp (signal path)
*
* Both paths share the same `state`, `argv`, `argc` variables,
* so the stack frame is preserved across the longjmp.
*/
if (setjmp(g_sigend_jmp_buf) == 0) {
/* Normal path — run the test */
signal(SIGPIPE, SIG_IGN); /* Ignore SIGPIPE for socket errors */
iperf_catch_sigend(sigend_handler);
/* Spawn reader thread to forward iperf output to Java */
if (pthread_create(&state->reader_thread, NULL,
reader_thread_func, state) != 0) {
free_argv(argv, argc);
close(pipefd[0]);
close(pipefd[1]);
const char *err = "Failed to start output reader thread";
LOGE("%s", err);
signal_error(state, err);
iperf_free_test(test);
g_test = NULL;
free(state);
return;
}
/* Notify Java that the test is starting */
signal_output(state, "[iPerf JNI] Starting iPerf3 client...\n");
/* Run the test */
g_stop = 0;
int ret = iperf_run_client(test);
/* Spawn reader thread to forward iperf output to Java */
if (pthread_create(&state->reader_thread, NULL,
reader_thread_func, state) != 0) {
free_argv(argv, total_argc);
close(pipefd[0]);
close(pipefd[1]);
const char *err = "Failed to start output reader thread";
LOGE("%s", err);
signal_error(state, err);
iperf_free_test(test);
g_test = NULL;
free(state);
return;
}
/* Wait for reader thread to finish */
pthread_join(state->reader_thread, NULL);
/* Run the test */
g_stop = 0;
int ret = iperf_run_client(test);
/* Flush and close output */
fflush(state->outfile);
fclose(state->outfile);
/* Clean up iperf */
iperf_free_test(test);
g_test = NULL;
/* Free argv */
free_argv(argv, argc);
/* Signal result to Java */
if (g_stop) {
signal_output(state, "[iPerf JNI] Test was stopped by user.\n");
} else if (ret < 0) {
char errbuf[256];
snprintf(errbuf, sizeof(errbuf), "[iPerf JNI] Test failed: %s\n",
iperf_strerror(i_errno));
signal_error(state, errbuf);
/*
* We get here after iperf_run_client returns normally.
* If a signal arrives during iperf_run_client(), the
* sigend_handler fires longjmp() and we never reach here.
*/
iperf_cleanup_and_signal(env, state, argv, total_argc, ret, 0);
} else {
signal_output(state, "[iPerf JNI] Test completed successfully.\n");
/*
* We got here via longjmp() from sigend_handler.
* Clean up resources allocated before the setjmp.
* NOTE: state, argv, argc are still valid on the stack.
*/
LOGI("Test interrupted by signal %d", g_signed_sig);
/* Stop flag for cleanup */
g_stop = 1;
/* Close the output file (the pipe write end) */
if (state->outfile) {
fclose(state->outfile);
}
/* Free argv (argv is still valid across longjmp since it's on stack) */
free_argv(argv, total_argc);
/* Run the cleanup with stopped=true.
* Note: argv is NULL, argc=0 so free_argv is a no-op.
* The state struct will be freed inside this function. */
iperf_cleanup_and_signal(env, state, NULL, 0, 0, 1);
}
/* Signal completion to Java */
signal_complete(state);
/* Free global ref and state struct */
(*env)->DeleteGlobalRef(env, state->callback_ref);
free(state);
}
/* ------------------------------------------------------------------ */
android/app/src/main/kotlin/com/novoyuuparosk/iperf3gui/IperfRunner.kt
+8 -1
View File
@@ -19,7 +19,14 @@ object IperfRunner : FlutterPlugin {
init {
// Load native library at class initialization
System.loadLibrary("iperf3jni")
try {
android.util.Log.i("IperfRunner", "Loading native library...")
System.loadLibrary("iperf3jni")
android.util.Log.i("IperfRunner", "Native library loaded successfully")
} catch (e: UnsatisfiedLinkError) {
android.util.Log.e("IperfRunner", "Failed to load native library: ${e.message}")
e.printStackTrace()
}
}
override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {