serve: Refactor some socket utility code into its own module.

We'll be using this in proxy mode later

src/sockutil.h

@@ -0,0 +1,32 @@
+#ifndef SOCKUTIL_H
+
+#define SOCKUTIL_H
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <arpa/inet.h>
+#include <netinet/tcp.h>
+
+/* Returns the size of the sockaddr, or 0 on error */
+size_t sockaddr_size(const struct sockaddr* sa);
+
+/* Convert a sockaddr into an address. Like inet_ntop, it returns dest if
+ * successful, NULL otherwise. In the latter case, dest will contain "???"
+ */
+const char* sockaddr_address_string(const struct sockaddr* sa, char* dest, size_t len);
+
+/* Set the SOL_REUSEADDR otion */
+int sock_set_reuseaddr(int fd, int optval);
+
+/* Set the tcp_nodelay option */
+int sock_set_tcp_nodelay(int fd, int optval);
+
+/* TODO: Set the tcp_cork option */
+// int sock_set_cork(int fd, int optval);
+
+/* Attempt to bind the fd to the sockaddr, retrying common transient failures */
+int sock_try_bind(int fd, const struct sockaddr* sa);
+
+#endif
+