F-4950: negate wolfIP error code when setting errno in POSIX shim macros

conditional_steal_call, conditional_steal_blocking_call and
wolfip_accept_common assigned the raw negative wolfIP return code to errno
(e.g. errno = -EINVAL) instead of its positive magnitude. Callers comparing
errno == EINVAL / ENOTCONN / ECONNRESET would silently mismatch. Negate the
value to match the adjacent hand-written paths (bind/close/sendto/send) and
the macros' own EAGAIN/wait-error branches.

Adds test-posix-errno which drives getpeername() through the
conditional_steal_call macro and asserts errno is a positive value.

Author: danielinux

Makefile

@@ -332,6 +332,17 @@ build/packet_ping: $(OBJ) build/port/posix/bsd_socket.o build/test/packet_ping.o
 	@echo "[LD] $@"
 	@$(CC) $(CFLAGS) -o $@ $(BEGIN_GROUP) $(^) $(LDFLAGS) $(END_GROUP)
 
+# F-4950 regression: test_posix_errno.c #includes bsd_socket.c directly, so the
+# shim object must not be linked again here.
+build/test-posix-errno: $(OBJ) build/test/test_posix_errno.o
+	@echo "[LD] $@"
+	@$(CC) $(CFLAGS) -o $@ $(BEGIN_GROUP) $(^) $(LDFLAGS) $(END_GROUP)
+
+.PHONY: posix-errno-test
+posix-errno-test: build/test-posix-errno
+	@echo "[RUN] $<"
+	@./build/test-posix-errno
+
 
 build/test-wolfssl:CFLAGS+=-Wno-cpp -DWOLFSSL_DEBUG -DWOLFSSL_WOLFIP
 build/test-httpd:CFLAGS+=-Wno-cpp -DWOLFSSL_DEBUG -DWOLFSSL_WOLFIP -Isrc/http

src/port/posix/bsd_socket.c

@@ -538,7 +538,7 @@ static int wolfip_wait_for_event_locked(struct wolfip_fd_entry *entry, short wai
         if (__wolfip_internal >= 0) { \
             int __wolfip_retval = wolfIP_sock_##call(IPSTACK, __wolfip_internal, ## __VA_ARGS__); \
             if (__wolfip_retval < 0) { \
-                errno = __wolfip_retval; \
+                errno = -__wolfip_retval; \
                 pthread_mutex_unlock(&wolfIP_mutex); \
                 return -1; \
             } \
@@ -585,7 +585,7 @@ static int wolfip_wait_for_event_locked(struct wolfip_fd_entry *entry, short wai
                 } \
             } while (__wolfip_retval == -EAGAIN); \
             if (__wolfip_retval < 0) { \
-                errno = __wolfip_retval; \
+                errno = -__wolfip_retval; \
                 pthread_mutex_unlock(&wolfIP_mutex); \
                 return -1; \
             } \
@@ -1544,7 +1544,7 @@ static int wolfip_accept_common(int sockfd, struct sockaddr *addr, socklen_t *ad
             }
         } while (internal_ret == -EAGAIN);
         if (internal_ret < 0) {
-            errno = internal_ret;
+            errno = -internal_ret;
             pthread_mutex_unlock(&wolfIP_mutex);
             return -1;
         }

src/test/test_posix_errno.c

@@ -0,0 +1,73 @@
+/* test_posix_errno.c
+ *
+ * Copyright (C) 2024 wolfSSL Inc.
+ *
+ * This file is part of wolfIP TCP/IP stack.
+ *
+ * wolfIP is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * wolfIP is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335, USA
+ */
+
+/* Regression test for F-4950: the POSIX shim macros must translate a negative
+ * wolfIP return code into a positive errno, exactly as the hand-written paths
+ * (bind/close/send/...) already do. Driving getpeername() through the
+ * conditional_steal_call() macro on a wolfIP-managed fd exercises the
+ * "errno = -ret" conversion: with the sign bug present errno is set to the raw
+ * negative code and the assertion below fails. */
+
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <netinet/in.h>
+
+/* Pull in the shim itself so we can reach its file-static state
+ * (in_the_stack / IPSTACK). The library constructor runs at load; without
+ * CAP_NET_ADMIN its TAP setup simply fails and returns, leaving the host_*
+ * passthrough pointers populated, which is all this test needs. */
+#include "../port/posix/bsd_socket.c"
+
+int main(void)
+{
+    struct sockaddr_in peer;
+    socklen_t peerlen = 0; /* deliberately too small -> internal error path */
+    int fd;
+    int ret;
+
+    /* The library constructor already initialised the static stack via
+     * wolfIP_init_static(); make sure it is present and take over the shim
+     * path so socket()/getpeername() are served by wolfIP, not libc. */
+    if (!IPSTACK)
+        wolfIP_init_static(&IPSTACK);
+    in_the_stack = 0;
+
+    fd = socket(AF_INET, SOCK_STREAM, 0);
+    assert(fd >= 0);
+
+    errno = 0;
+    memset(&peer, 0, sizeof(peer));
+    ret = getpeername(fd, (struct sockaddr *)&peer, &peerlen);
+
+    printf("getpeername ret=%d errno=%d (%s)\n", ret, errno,
+           errno > 0 ? strerror(errno) : "negative/raw");
+
+    /* The call must fail... */
+    assert(ret == -1);
+    /* ...and errno must be a real positive errno value, never the raw negative
+     * wolfIP code (the F-4950 defect). */
+    assert(errno > 0);
+
+    printf("F-4950 regression test passed\n");
+    return 0;
+}