MAJOR: listener: support inheriting a listening fd from the parent
Using the address syntax "fd@<num>", a listener may inherit a file
descriptor that the caller process has already bound and passed as
this number. The fd's socket family is detected using getsockname(),
and the usual initialization is performed through the existing code
for that family, but the socket creation is skipped.
Whether the parent has performed the listen() call or not is not
important as this is detected.
For UNIX sockets, we immediately clear the path after preparing a
socket so that we never remove it in case an abort would happen due
to a late error during startup.
diff --git a/src/standard.c b/src/standard.c
index c670be0..cc22ba7 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -632,6 +632,7 @@
* - "ipv6@" => force address to resolve as IPv6 and fail if not possible.
* - "unix@" => force address to be a path to a UNIX socket even if the
* path does not start with a '/'
+ * - "fd@" => an integer must follow, and is a file descriptor number.
*
* Also note that in order to avoid any ambiguity with IPv6 addresses, the ':'
* is mandatory after the IP address even when no port is specified. NULL is
@@ -640,6 +641,9 @@
*
* If <pfx> is non-null, it is used as a string prefix before any path-based
* address (typically the path to a unix socket).
+ *
+ * When a file descriptor is passed, its value is put into the s_addr part of
+ * the address when cast to sockaddr_in and the address family is AF_UNSPEC.
*/
struct sockaddr_storage *str2sa_range(const char *str, int *low, int *high, char **err, const char *pfx)
{
@@ -677,7 +681,21 @@
else
ss.ss_family = AF_UNSPEC;
+ if (ss.ss_family == AF_UNSPEC && strncmp(str2, "fd@", 3) == 0) {
+ char *endptr;
+
+ str2 += 3;
+ ((struct sockaddr_in *)&ss)->sin_addr.s_addr = strtol(str2, &endptr, 10);
+
- if (ss.ss_family == AF_UNIX) {
+ if (!*str2 || *endptr) {
+ memprintf(err, "file descriptor '%s' is not a valid integer\n", str2);
+ goto out;
+ }
+
+ /* we return AF_UNSPEC if we use a file descriptor number */
+ ss.ss_family = AF_UNSPEC;
+ }
+ else if (ss.ss_family == AF_UNIX) {
int prefix_path_len;
int max_path_len;