socket: Set SO_REUSEPORT before bind()

bind() fails if it is called before setting SO_REUSEPORT and another
process is already binded to the same addess.

A new reuse_port option has been introduced to socket_address_listen()
to set the option as part of socket initialization.

3 files changed, 10 insertions, 7 deletions

diff --git a/src/basic/socket-label.c b/src/basic/socket-label.c
index cbe3ff216e..144e6fd86e 100644
--- a/src/basic/socket-label.c
+++ b/src/basic/socket-label.c
@@ -38,6 +38,7 @@ int socket_address_listen(
                 int backlog,
                 SocketAddressBindIPv6Only only,
                 const char *bind_to_device,
+                bool reuse_port,
                 bool free_bind,
                 bool transparent,
                 mode_t directory_mode,
@@ -83,6 +84,12 @@ int socket_address_listen(
                         if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, bind_to_device, strlen(bind_to_device)+1) < 0)
                                 return -errno;
 
+                if (reuse_port) {
+                        one = 1;
+                        if (setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)) < 0)
+                                log_warning_errno(errno, "SO_REUSEPORT failed: %m");
+                }
+
                 if (free_bind) {
                         one = 1;
                         if (setsockopt(fd, IPPROTO_IP, IP_FREEBIND, &one, sizeof(one)) < 0)
@@ -146,7 +153,7 @@ int make_socket_fd(int log_level, const char* address, int flags) {
         }
 
         fd = socket_address_listen(&a, flags, SOMAXCONN, SOCKET_ADDRESS_DEFAULT,
-                                   NULL, false, false, 0755, 0644, NULL);
+                                   NULL, false, false, false, 0755, 0644, NULL);
         if (fd < 0 || log_get_max_level() >= log_level) {
                 _cleanup_free_ char *p = NULL;
 
diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
index 538cf59174..6b0ce7836f 100644
--- a/src/basic/socket-util.h
+++ b/src/basic/socket-util.h
@@ -80,6 +80,7 @@ int socket_address_listen(
                 int backlog,
                 SocketAddressBindIPv6Only only,
                 const char *bind_to_device,
+                bool reuse_port,
                 bool free_bind,
                 bool transparent,
                 mode_t directory_mode,
diff --git a/src/core/socket.c b/src/core/socket.c
index d3178e642b..693cbc6080 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -922,12 +922,6 @@ static void socket_apply_socket_options(Socket *s, int fd) {
                 if (setsockopt(fd, SOL_TCP, TCP_CONGESTION, s->tcp_congestion, strlen(s->tcp_congestion)+1) < 0)
                         log_unit_warning_errno(UNIT(s), errno, "TCP_CONGESTION failed: %m");
 
-        if (s->reuse_port) {
-                int b = s->reuse_port;
-                if (setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &b, sizeof(b)) < 0)
-                        log_unit_warning_errno(UNIT(s), errno, "SO_REUSEPORT failed: %m");
-        }
-
         if (s->smack_ip_in) {
                 r = mac_smack_apply_ip_in_fd(fd, s->smack_ip_in);
                 if (r < 0)
@@ -1183,6 +1177,7 @@ static int socket_open_fds(Socket *s) {
                                         s->backlog,
                                         s->bind_ipv6_only,
                                         s->bind_to_device,
+                                        s->reuse_port,
                                         s->free_bind,
                                         s->transparent,
                                         s->directory_mode,