[misc] Use fcntl+O_NONBLOCK when binding instead of socket+SOCK_NONBLOCK

socket() with SOCK_NONBLOCK (O_NONBLOCK) seems not to be possible on MacOS, it
yields 'Protocol wrong type for socket'. Switch to using fcntl() and O_NONBLOCK
instead, hopefully works better cross-platform.

Closes #1644

src/httpd_libevhttp.c

@@ -359,7 +359,7 @@ httpd_server_new(struct event_base *evbase, unsigned short port, httpd_request_c
   server->request_cb = cb;
   server->request_cb_arg = arg;
 
-  server->fd = net_bind_with_reuseport(&port, SOCK_STREAM | SOCK_NONBLOCK, "httpd");
+  server->fd = net_bind_with_reuseport(&port, SOCK_STREAM, "httpd");
   if (server->fd <= 0)
     goto error;
 

src/mdns_avahi.c

@@ -35,6 +35,7 @@
 #include <arpa/inet.h>
 #include <net/if.h>
 #include <unistd.h>
+#include <fcntl.h>
 
 #include <event2/event.h>
 
@@ -584,6 +585,7 @@ connection_test(int family, const char *address, const char *address_log, int po
   fd_set fdset;
   struct timeval timeout = { MDNS_CONNECT_TEST_TIMEOUT, 0 };
   socklen_t len;
+  int flags;
   int error;
   int retval;
   int ret;
@@ -603,13 +605,29 @@ connection_test(int family, const char *address, const char *address_log, int po
       return -1;
     }
 
-  sock = socket(ai->ai_family, ai->ai_socktype | SOCK_NONBLOCK, ai->ai_protocol);
+  sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
   if (sock < 0)
     {
       DPRINTF(E_WARN, L_MDNS, "Connection test to %s:%d failed with socket error: %s\n", address_log, port, strerror(errno));
       goto out_free_ai;
     }
 
+  // For Linux we could just give SOCK_NONBLOCK to socket(), but that won't work
+  // with MacOS, so we have to use fcntl()
+  flags = fcntl(sock, F_GETFL, 0);
+  if (flags < 0)
+    {
+      DPRINTF(E_WARN, L_MDNS, "Connection test to %s:%d failed with fcntl get flags error: %s\n", address_log, port, strerror(errno));
+      goto out_close_socket;
+    }
+
+  ret = fcntl(sock, F_SETFL, flags | O_NONBLOCK);
+  if (ret < 0)
+    {
+      DPRINTF(E_WARN, L_MDNS, "Connection test to %s:%d failed with fcntl set flags error: %s\n", address_log, port, strerror(errno));
+      goto out_close_socket;
+    }
+
   ret = connect(sock, ai->ai_addr, ai->ai_addrlen);
   if (ret < 0 && errno != EINPROGRESS)
     {

src/misc.c

@@ -48,6 +48,7 @@
 # include <pthread_np.h>
 #endif
 
+#include <fcntl.h>
 #include <netdb.h>
 #include <arpa/inet.h>
 #include <ifaddrs.h> // getifaddrs
@@ -222,19 +223,20 @@ net_if_get(char *ifname, size_t ifname_len, const char *addr)
   return (ifname[0] != 0) ? 0 : -1;
 }
 
-int
+static int
-net_connect(const char *addr, unsigned short port, int type, const char *log_service_name)
+net_connect_impl(const char *addr, unsigned short port, int type, const char *log_service_name, bool set_nonblock)
 {
   struct addrinfo hints = { 0 };
   struct addrinfo *servinfo;
   struct addrinfo *ptr;
   char strport[8];
+  int flags;
   int fd;
   int ret;
 
   DPRINTF(E_DBG, L_MISC, "Connecting to '%s' at %s (port %u)\n", log_service_name, addr, port);
 
-  hints.ai_socktype = (type & (SOCK_STREAM | SOCK_DGRAM)); // filter since type can be SOCK_STREAM | SOCK_NONBLOCK
+  hints.ai_socktype = type;
   hints.ai_family = (cfg_getbool(cfg_getsec(cfg, "general"), "ipv6")) ? AF_UNSPEC : AF_INET;
 
   snprintf(strport, sizeof(strport), "%hu", port);
@@ -247,14 +249,26 @@ net_connect(const char *addr, unsigned short port, int type, const char *log_ser
 
   for (ptr = servinfo; ptr; ptr = ptr->ai_next)
     {
-      fd = socket(ptr->ai_family, type | SOCK_CLOEXEC, ptr->ai_protocol);
+      fd = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
       if (fd < 0)
 	{
 	  continue;
 	}
 
+      // For Linux we could just give SOCK_CLOEXEC to socket(), but that won't
+      // work with MacOS, so we have to use fcntl()
+      flags = fcntl(fd, F_GETFL, 0);
+      if (flags < 0)
+	continue;
+      if (set_nonblock)
+	ret = fcntl(fd, F_SETFL, flags | O_NONBLOCK | O_CLOEXEC);
+      else
+	ret = fcntl(fd, F_SETFL, flags | O_CLOEXEC);
+      if (ret < 0)
+	continue;
+
       ret = connect(fd, ptr->ai_addr, ptr->ai_addrlen);
-      if (ret < 0 && errno != EINPROGRESS) // EINPROGRESS in case of SOCK_NONBLOCK
+      if (ret < 0 && errno != EINPROGRESS) // EINPROGRESS in case of nonblock
 	{
 	  close(fd);
 	  continue;
@@ -276,8 +290,15 @@ net_connect(const char *addr, unsigned short port, int type, const char *log_ser
   return fd;
 }
 
+int
+net_connect(const char *addr, unsigned short port, int type, const char *log_service_name)
+{
+  return net_connect_impl(addr, port, type, log_service_name, false);
+}
+
 // If *port is 0 then a random port will be assigned, and *port will be updated
-// with the port number
+// with the port number. SOCK_STREAM type services are set to use non-blocking
+// sockets.
 static int
 net_bind_impl(short unsigned *port, int type, const char *log_service_name, bool reuseport)
 {
@@ -289,6 +310,7 @@ net_bind_impl(short unsigned *port, int type, const char *log_service_name, bool
   const char *cfgaddr;
   char addr[INET6_ADDRSTRLEN];
   char strport[8];
+  int flags;
   int yes = 1;
   int no = 0;
   int fd = -1;
@@ -296,7 +318,7 @@ net_bind_impl(short unsigned *port, int type, const char *log_service_name, bool
 
   cfgaddr = cfg_getstr(cfg_getsec(cfg, "general"), "bind_address");
 
-  hints.ai_socktype = (type & (SOCK_STREAM | SOCK_DGRAM)); // filter since type can be SOCK_STREAM | SOCK_NONBLOCK
+  hints.ai_socktype = type;
   hints.ai_family = (cfg_getbool(cfg_getsec(cfg, "general"), "ipv6")) ? AF_INET6 : AF_INET;
   hints.ai_flags = cfgaddr ? 0 : AI_PASSIVE;
 
@@ -313,10 +335,22 @@ net_bind_impl(short unsigned *port, int type, const char *log_service_name, bool
       if (fd >= 0)
 	close(fd);
 
-      fd = socket(ptr->ai_family, type | SOCK_CLOEXEC, ptr->ai_protocol);
+      fd = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
       if (fd < 0)
 	continue;
 
+      // For Linux we could just give SOCK_NONBLOCK and SOCK_CLOEXEC to
+      // socket(), but that won't work with MacOS, so we have to use fcntl()
+      flags = fcntl(fd, F_GETFL, 0);
+      if (flags < 0)
+	continue;
+      if (type == SOCK_STREAM)
+	ret = fcntl(fd, F_SETFL, flags | O_NONBLOCK | O_CLOEXEC);
+      else
+	ret = fcntl(fd, F_SETFL, flags | O_CLOEXEC);
+      if (ret < 0)
+	continue;
+
       // Makes us able to attach multiple threads to the same port
       if (reuseport)
 	ret = setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &yes, sizeof(yes));

src/misc.h

@@ -15,15 +15,6 @@
 #include <sys/socket.h>
 #include <netinet/in.h>
 
-#ifndef SOCK_NONBLOCK
-#include <fcntl.h>
-#define SOCK_NONBLOCK O_NONBLOCK
-#endif
-
-#ifndef SOCK_CLOEXEC
-#define SOCK_CLOEXEC 0
-#endif
-
 union net_sockaddr
 {
   struct sockaddr_in sin;

src/mpd.c

@@ -4813,7 +4813,7 @@ mpd_init(void)
   CHECK_NULL(L_MPD, evbase_mpd = event_base_new());
   CHECK_NULL(L_MPD, cmdbase = commands_base_new(evbase_mpd, NULL));
 
-  mpd_sockfd = net_bind(&port, SOCK_STREAM | SOCK_NONBLOCK, "mpd");
+  mpd_sockfd = net_bind(&port, SOCK_STREAM, "mpd");
   if (mpd_sockfd < 0)
     {
       DPRINTF(E_LOG, L_MPD, "Could not bind mpd server to port %hu\n", port);