MEDIUM: sock_inet: implement sock_inet_bind_receiver()

This function collects all the receiver-specific code from both
tcp_bind_listener() and udp_bind_listener() in order to provide a more
generic AF_INET/AF_INET6 socket binding function. For now the API is
not very elegant because some info are still missing from the receiver
while there's no ideal place to fill them except when calling ->listen()
at the protocol level. It looks like some polishing code is needed in
check_config_validity() or somewhere around this in order to finalize
the receivers' setup. The main issue is that listeners and receivers
are created *before* bind_conf options are parsed and that there's no
finishing step to resolve some of them.

The function currently sets up a receiver and subscribes it to the
poller. In an ideal world we wouldn't subscribe it but let the caller
do it after having finished to configure the L4 stuff. The problem is
that the caller would then need to perform an fd_insert() call and to
possibly set the exported flag on the FD while it's not its job. Maybe
an improvement could be to have a separate sock_start_receiver() call
in sock.c.

For now the function is not used but it will soon be. It's already
referenced as tcp and udp's ->bind().

include/haproxy/sock_inet.h

@@ -37,5 +37,6 @@ int sock_inet_get_dst(int fd, struct sockaddr *sa, socklen_t salen, int dir);
 int sock_inet_is_foreign(int fd, sa_family_t family);
 int sock_inet4_make_foreign(int fd);
 int sock_inet6_make_foreign(int fd);
+int sock_inet_bind_receiver(struct receiver *rx, void (*handler)(int fd), char **errmsg);
 
 #endif /* _HAPROXY_SOCK_INET_H */

src/proto_tcp.c

@@ -59,6 +59,7 @@ static struct protocol proto_tcpv4 = {
 	.l3_addrlen = 32/8,
 	.accept = &listener_accept,
 	.connect = tcp_connect_server,
+	.bind = sock_inet_bind_receiver,
 	.listen = tcp_bind_listener,
 	.enable_all = enable_all_listeners,
 	.get_src = sock_get_src,
@@ -83,6 +84,7 @@ static struct protocol proto_tcpv6 = {
 	.l3_addrlen = 128/8,
 	.accept = &listener_accept,
 	.connect = tcp_connect_server,
+	.bind = sock_inet_bind_receiver,
 	.listen = tcp_bind_listener,
 	.enable_all = enable_all_listeners,
 	.get_src = sock_get_src,

src/proto_udp.c

@@ -55,6 +55,7 @@ static struct protocol proto_udp4 = {
 	.l3_addrlen = 32/8,
 	.accept = NULL,
 	.connect = NULL,
+	.bind = sock_inet_bind_receiver,
 	.listen = udp_bind_listener,
 	.enable_all = enable_all_listeners,
 	.get_src = udp_get_src,
@@ -79,6 +80,7 @@ static struct protocol proto_udp6 = {
 	.l3_addrlen = 128/8,
 	.accept = NULL,
 	.connect = NULL,
+	.bind = sock_inet_bind_receiver,
 	.listen = udp_bind_listener,
 	.enable_all = enable_all_listeners,
 	.get_src = udp6_get_src,

src/sock_inet.c

@@ -10,7 +10,9 @@
  *
  */
 
+#include <fcntl.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <sys/param.h>
 #include <sys/socket.h>
@@ -20,7 +22,12 @@
 #include <netinet/in.h>
 
 #include <haproxy/api.h>
+#include <haproxy/errors.h>
+#include <haproxy/fd.h>
 #include <haproxy/global.h>
+#include <haproxy/namespace.h>
+#include <haproxy/receiver-t.h>
+#include <haproxy/sock.h>
 #include <haproxy/sock_inet.h>
 #include <haproxy/tools.h>
 
@@ -221,6 +228,151 @@ int sock_inet6_make_foreign(int fd)
 		0;
 }
 
+/* Binds receiver <rx>, and assigns <handler> and rx->owner as the callback and
+ * context, respectively. Returns and error code made of ERR_* bits on failure
+ * or ERR_NONE on success. On failure, an error message may be passed into
+ * <errmsg>.
+ */
+int sock_inet_bind_receiver(struct receiver *rx, void (*handler)(int fd), char **errmsg)
+{
+	int fd, err, ext;
+	/* copy listener addr because sometimes we need to switch family */
+	struct sockaddr_storage addr_inet = rx->addr;
+
+	/* force to classic sock family, not AF_CUST_* */
+	addr_inet.ss_family = rx->proto->sock_family;
+
+	/* ensure we never return garbage */
+	if (errmsg)
+		*errmsg = 0;
+
+	err = ERR_NONE;
+
+	if (rx->flags & RX_F_BOUND)
+		return ERR_NONE;
+
+	/* if no FD was assigned yet, we'll have to either find a compatible
+	 * one or create a new one.
+	 */
+	if (rx->fd == -1)
+		rx->fd = sock_find_compatible_fd(rx);
+
+	/* if the receiver now has an fd assigned, then we were offered the fd
+	 * by an external process (most likely the parent), and we don't want
+	 * to create a new socket. However we still want to set a few flags on
+	 * the socket.
+	 */
+	fd = rx->fd;
+	ext = (fd >= 0);
+
+	if (!ext) {
+		fd = my_socketat(rx->settings->netns, rx->proto->sock_family,
+		                 rx->proto->sock_type, rx->proto->sock_prot);
+		if (fd == -1) {
+			err |= ERR_RETRYABLE | ERR_ALERT;
+			memprintf(errmsg, "cannot create receiving socket");
+			goto bind_return;
+		}
+	}
+
+	if (fd >= global.maxsock) {
+		err |= ERR_FATAL | ERR_ABORT | ERR_ALERT;
+		memprintf(errmsg, "not enough free sockets (raise '-n' parameter)");
+		goto bind_close_return;
+	}
+
+	if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1) {
+		err |= ERR_FATAL | ERR_ALERT;
+		memprintf(errmsg, "cannot make socket non-blocking");
+		goto bind_close_return;
+	}
+
+	if (!ext && setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)) == -1) {
+		/* not fatal but should be reported */
+		memprintf(errmsg, "cannot do so_reuseaddr");
+		err |= ERR_ALERT;
+	}
+
+#ifdef SO_REUSEPORT
+	/* OpenBSD and Linux 3.9 support this. As it's present in old libc versions of
+	 * Linux, it might return an error that we will silently ignore.
+	 */
+	if (!ext && (global.tune.options & GTUNE_USE_REUSEPORT))
+		setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one));
+#endif
+
+	if (!ext && (rx->settings->options & RX_O_FOREIGN)) {
+		switch (addr_inet.ss_family) {
+		case AF_INET:
+			if (!sock_inet4_make_foreign(fd)) {
+				memprintf(errmsg, "cannot make receiving socket transparent");
+				err |= ERR_ALERT;
+			}
+		break;
+		case AF_INET6:
+			if (!sock_inet6_make_foreign(fd)) {
+				memprintf(errmsg, "cannot make receiving socket transparent");
+				err |= ERR_ALERT;
+			}
+		break;
+		}
+	}
+
+#ifdef SO_BINDTODEVICE
+	/* Note: this might fail if not CAP_NET_RAW */
+	if (!ext && rx->settings->interface) {
+		if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
+		               rx->settings->interface,
+		               strlen(rx->settings->interface) + 1) == -1) {
+			memprintf(errmsg, "cannot bind receiver to device");
+			err |= ERR_WARN;
+		}
+	}
+#endif
+
+#if defined(IPV6_V6ONLY)
+	if (addr_inet.ss_family == AF_INET6 && !ext) {
+		/* Prepare to match the v6only option against what we really want. Note
+		 * that sadly the two options are not exclusive to each other and that
+		 * v6only is stronger than v4v6.
+		 */
+		if ((rx->settings->options & RX_O_V6ONLY) ||
+		    (sock_inet6_v6only_default && !(rx->settings->options & RX_O_V4V6)))
+			setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
+		else
+			setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &zero, sizeof(zero));
+	}
+#endif
+
+	if (!ext && bind(fd, (struct sockaddr *)&addr_inet, rx->proto->sock_addrlen) == -1) {
+		err |= ERR_RETRYABLE | ERR_ALERT;
+		memprintf(errmsg, "cannot bind socket");
+		goto bind_close_return;
+	}
+
+	rx->fd = fd;
+	rx->flags |= RX_F_BOUND;
+
+	fd_insert(fd, rx->owner, handler, thread_mask(rx->settings->bind_thread) & all_threads_mask);
+
+	/* for now, all regularly bound TCP listeners are exportable */
+	if (!(rx->flags & RX_F_INHERITED))
+		fdtab[fd].exported = 1;
+
+ bind_return:
+	if (errmsg && *errmsg) {
+		char pn[INET6_ADDRSTRLEN];
+
+		addr_to_str(&addr_inet, pn, sizeof(pn));
+		memprintf(errmsg, "%s [%s:%d]", *errmsg, pn, get_host_port(&addr_inet));
+	}
+	return err;
+
+ bind_close_return:
+	close(fd);
+	goto bind_return;
+}
+
 static void sock_inet_prepare()
 {
 	int fd, val;