tree-wide: introduce new SOCKADDR_UN_LEN() macro, and use it everywhere

The macro determines the right length of a AF_UNIX "struct sockaddr_un" to pass to
connect() or bind(). It automatically figures out if the socket refers to an
abstract namespace socket, or a socket in the file system, and properly handles
the full length of the path field.

This macro is not only safer, but also simpler to use, than the usual
offsetof() + strlen() logic.

1 files changed, 3 insertions, 4 deletions

diff --git a/src/tty-ask-password-agent/tty-ask-password-agent.c b/src/tty-ask-password-agent/tty-ask-password-agent.c
index c7ded451a2..ee879c7b89 100644
--- a/src/tty-ask-password-agent/tty-ask-password-agent.c
+++ b/src/tty-ask-password-agent/tty-ask-password-agent.c
@@ -65,8 +65,8 @@ static int ask_password_plymouth(
                 const char *flag_file,
                 char ***ret) {
 
+        static const union sockaddr_union sa = PLYMOUTH_SOCKET;
         _cleanup_close_ int fd = -1, notify = -1;
-        union sockaddr_union sa = PLYMOUTH_SOCKET;
         _cleanup_free_ char *packet = NULL;
         ssize_t k;
         int r, n;
@@ -94,7 +94,7 @@ static int ask_password_plymouth(
         if (fd < 0)
                 return -errno;
 
-        r = connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + 1 + strlen(sa.un.sun_path+1));
+        r = connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (r < 0)
                 return -errno;
 
@@ -269,8 +269,7 @@ static int send_passwords(const char *socket_name, char **passwords) {
 
         strncpy(sa.un.sun_path, socket_name, sizeof(sa.un.sun_path));
 
-        r = sendto(socket_fd, packet, packet_length, MSG_NOSIGNAL, &sa.sa,
-                   offsetof(struct sockaddr_un, sun_path) + strlen(socket_name));
+        r = sendto(socket_fd, packet, packet_length, MSG_NOSIGNAL, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (r < 0)
                 r = log_debug_errno(errno, "sendto(): %m");