feat: add support for accept and accept4

Since the socket address of the accepted socket is unknown,
all bytes are set to zero and the length is truncated to the size
of the generic `struct sockaddr`.

Signed-off-by: Harald Hoyer <[email protected]>

Author: haraldh

expected/wasm32-wasi/defined-symbols.txt

@@ -363,6 +363,8 @@ _start
 a64l
 abort
 abs
+accept
+accept4
 access
 acos
 acosf

libc-bottom-half/sources/accept.c

@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: BSD-2-Clause
+
+#include <sys/socket.h>
+
+#include <assert.h>
+#include <wasi/api.h>
+#include <errno.h>
+#include <string.h>
+
+int accept(int socket, struct sockaddr *restrict addr, socklen_t *restrict addrlen) {
+  int ret = -1;
+
+  __wasi_errno_t error = __wasi_sock_accept(socket, 0, &ret);
+
+  if (error != 0) {
+    errno = error;
+    return -1;
+  }
+
+  // Clear sockaddr to indicate undefined address
+  memset(addr, 0, *addrlen);
+  // might be AF_UNIX or AF_INET
+  addr->sa_family = AF_UNSPEC;
+  *addrlen = sizeof(struct sockaddr);
+
+  return ret;
+}
+
+int accept4(int socket, struct sockaddr *restrict addr, socklen_t *restrict addrlen, int flags) {
+  int ret = -1;
+
+  if (flags & ~(SOCK_NONBLOCK | SOCK_CLOEXEC)) {
+    errno = EINVAL;
+    return -1;
+  }
+
+  __wasi_errno_t error = __wasi_sock_accept(socket, (flags & SOCK_NONBLOCK) ? __WASI_FDFLAGS_NONBLOCK : 0, &ret);
+
+  if (error != 0) {
+    errno = error;
+    return -1;
+  }
+
+  // Clear sockaddr to indicate undefined address
+  memset(addr, 0, *addrlen);
+  // might be AF_UNIX or AF_INET
+  addr->sa_family = AF_UNSPEC;
+  *addrlen = sizeof(struct sockaddr);
+
+  return ret;
+}

libc-top-half/musl/include/sys/socket.h

@@ -404,9 +404,10 @@ int shutdown (int, int);
 int bind (int, const struct sockaddr *, socklen_t);
 int connect (int, const struct sockaddr *, socklen_t);
 int listen (int, int);
+#endif
+
 int accept (int, struct sockaddr *__restrict, socklen_t *__restrict);
 int accept4(int, struct sockaddr *__restrict, socklen_t *__restrict, int);
-#endif
 
 #ifdef __wasilibc_unmodified_upstream /* WASI has no getsockname/getpeername */
 int getsockname (int, struct sockaddr *__restrict, socklen_t *__restrict);