SO_ERROR
if ((ret = getsockopt(s, SOL_SOCKET, SO_ERROR,
if (getsockopt(sock, SOL_SOCKET, SO_ERROR, &err, &len) != 0)
if (getsockopt(c->sock, SOL_SOCKET, SO_ERROR, &err, &sz) == -1) {
if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) {
case SO_ERROR: