[EventEngine] fix bug in unix-abstract socket URI processing (#33721)

URI should be resolved to unix abstract only if the first byte is NULL
but the path length is > 1 (i.e there is more than one byte in the
path). Otherwise treat is as unix URI.

Moreover, when the AsyncConnectionAcceptor is destroyed, if it was
managing a unix domain socket, then the socket should be unlinked to
ensure we dont leave the underlying file hanging around forever.

src/core/lib/event_engine/posix_engine/posix_engine_listener.cc

@@ -182,11 +182,11 @@ void PosixEngineListenerImpl::AsyncConnectionAcceptor::NotifyOnAccept(
     }
 
     // For UNIX sockets, the accept call might not fill up the member
-    // sun_path of sockaddr_un, so explicitly call getsockname to get it.
+    // sun_path of sockaddr_un, so explicitly call getpeername to get it.
     if (addr.address()->sa_family == AF_UNIX) {
       socklen_t len = EventEngine::ResolvedAddress::MAX_SIZE_BYTES;
-      if (getsockname(fd, const_cast<sockaddr*>(addr.address()), &len) < 0) {
-        gpr_log(GPR_ERROR, "Closing acceptor. Failed getsockname: %s",
+      if (getpeername(fd, const_cast<sockaddr*>(addr.address()), &len) < 0) {
+        gpr_log(GPR_ERROR, "Closing acceptor. Failed getpeername: %s",
                 strerror(errno));
         close(fd);
         // Shutting down the acceptor. Unref the ref grabbed in

src/core/lib/event_engine/posix_engine/posix_engine_listener.h

@@ -110,6 +110,8 @@ class PosixEngineListenerImpl
     }
     ListenerSocketsContainer::ListenerSocket& Socket() { return socket_; }
     ~AsyncConnectionAcceptor() {
+      // If uds socket, unlink it so that the corresponding file is deleted.
+      UnlinkIfUnixDomainSocket(*socket_.sock.LocalAddress());
       handle_->OrphanHandle(nullptr, nullptr, "");
       delete notify_on_accept_;
     }

src/core/lib/event_engine/tcp_socket_utils.cc

@@ -100,12 +100,11 @@ absl::StatusOr<std::string> ResolvedAddrToUnixPathIfPossible(
 #else
   int len = resolved_addr->size() - sizeof(unix_addr->sun_family) - 1;
 #endif
-  bool abstract = (len < 0 || unix_addr->sun_path[0] == '\0');
+  if (len <= 0) return "";
   std::string path;
-  if (abstract) {
-    if (len >= 0) {
-      path = std::string(unix_addr->sun_path + 1, len);
-    }
+  if (unix_addr->sun_path[0] == '\0') {
+    // unix-abstract socket processing.
+    path = std::string(unix_addr->sun_path + 1, len);
     path = absl::StrCat(std::string(1, '\0'), path);
   } else {
     size_t maxlen = sizeof(unix_addr->sun_path);
@@ -123,9 +122,9 @@ absl::StatusOr<std::string> ResolvedAddrToUriUnixIfPossible(
   GRPC_RETURN_IF_ERROR(path.status());
   std::string scheme;
   std::string path_string;
-  if (path->at(0) == '\0') {
+  if (!path->empty() && path->at(0) == '\0' && path->length() > 1) {
     scheme = "unix-abstract";
-    path_string = path->length() > 1 ? path->substr(1, std::string::npos) : "";
+    path_string = path->substr(1, std::string::npos);
   } else {
     scheme = "unix";
     path_string = std::move(*path);