Exercise STCP writes with default SIGPIPE disposition

tests/Makefile.am

@@ -100,6 +100,7 @@ if OS_LINUX
 check_PROGRAMS += \
     test_ntp_regressions \
     test_etcp_windows \
+    test_stcp_sigpipe \
     test_firewall \
     test_mem \
     test_config_updater \
@@ -1011,6 +1012,8 @@ test_etcp_session_LDADD = $(LIBUTUN) $(COMMON_LIBS)
 test_etcp_session_LDFLAGS = $(test_clock_ldflags)
 
 test_etcp_windows_SOURCES = test_etcp_windows.c $(test_clock_sources)
+test_stcp_sigpipe_SOURCES = test_stcp_sigpipe.c
+test_stcp_sigpipe_LDADD = $(LIBUTUN) $(COMMON_LIBS)
 test_etcp_windows_LDADD = $(LIBUTUN) $(COMMON_LIBS)
 test_etcp_windows_LDFLAGS = $(test_clock_ldflags) -Wl,--wrap=etcp_encrypt_send -Wl,--wrap=memory_pool_alloc_impl \
     -Wl,--wrap=bbr_main -Wl,--wrap=uasync_set_timeout -Wl,--wrap=uasync_call_soon

tests/test_stcp_sigpipe.c

@@ -0,0 +1,45 @@
+/* SIGPIPE остаётся с действием по умолчанию: оба пути STCP обязаны вернуть ошибку закрытого пира. */
+#include "stcp.h"
+#include "../lib/platform_compat.h"
+#include "../lib/mem.h"
+#include <signal.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+
+#define CHECK(x) do { if (!(x)) { DEBUG_ERROR(DEBUG_CATEGORY_GENERAL, "FAIL %s:%d: %s", __func__, __LINE__, #x); exit(1); } } while (0)
+
+static void check_closed_peer(int buffered) {
+    int sockets[2]; CHECK(socketpair(AF_UNIX, SOCK_STREAM, 0, sockets) == 0);
+    CHECK(socket_close_wrapper(sockets[1]) == 0);
+    struct UASYNC* ua = uasync_create(); CHECK(ua);
+    struct stcp_conn conn = {.ua = ua, .sock = sockets[0], .state = STCP_STATE_DATA};
+    uint8_t* bytes = u_malloc(16); CHECK(bytes); memset(bytes, 0, 16);
+    if (buffered) {
+        conn.send_buf = bytes; conn.send_len = 16;
+        stcp_write_cb(conn.sock, &conn);
+        CHECK(conn.close_err == EPIPE && conn.close_call_soon);
+        uasync_drain_immediate(ua);
+        CHECK(conn.state == STCP_STATE_CLOSED && !conn.send_buf);
+    } else {
+        CHECK(stcp_send_raw(&conn, bytes, 16) < 0 && socket_get_error() == EPIPE);
+        u_free(bytes); stcp_conn_do_close(&conn, EPIPE);
+    }
+    uasync_poll(ua, 0); CHECK(ua->timer_alloc_count == ua->timer_free_count);
+    uasync_destroy(ua, 0);
+}
+
+int main(void) {
+    debug_config_init(); debug_set_level(DEBUG_LEVEL_ERROR);
+    for (int buffered = 0; buffered < 2; buffered++) {
+        pid_t child = fork(); CHECK(child >= 0);
+        if (!child) {
+            CHECK(signal(SIGPIPE, SIG_DFL) != SIG_ERR);
+            size_t baseline = u_get_allocated_count();
+            check_closed_peer(buffered); CHECK(u_get_allocated_count() == baseline);
+            exit(0);
+        }
+        int status; CHECK(waitpid(child, &status, 0) == child);
+        CHECK(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+    }
+    return 0;
+}