FreeBSD 8.0's <net/if.h> requires <sys/socket.h> to be included first,
even though I don't see any such requirement in POSIX.
 #include <fcntl.h>
 #include <inttypes.h>
 #include <netinet/in.h>
+#include <sys/socket.h>
 #include <net/if.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "discovery.h"
 #include <errno.h>
 #include <inttypes.h>
+#include <sys/socket.h>
 #include <net/if.h>
 #include <regex.h>
 #include <stdlib.h>
 
 #include <arpa/inet.h>
 #include <errno.h>
 #include <inttypes.h>
+#include <sys/socket.h>
 #include <net/if.h>
 #include <string.h>
 #include <stdlib.h>
 
 #include "ofproto.h"
 #include <errno.h>
 #include <inttypes.h>
+#include <sys/socket.h>
 #include <net/if.h>
 #include <netinet/in.h>
 #include <stdbool.h>
 
 #include <errno.h>
 #include <getopt.h>
 #include <inttypes.h>
+#include <sys/socket.h>
 #include <net/if.h>
 #include <netinet/in.h>
 #include <signal.h>
 
 #include <errno.h>
 #include <getopt.h>
 #include <inttypes.h>
+#include <sys/socket.h>
 #include <net/if.h>
 #include <netinet/in.h>
 #include <signal.h>
 
 #include <arpa/inet.h>
 #include <ctype.h>
 #include <inttypes.h>
+#include <sys/socket.h>
 #include <net/if.h>
 #include <openflow/openflow.h>
 #include <signal.h>