MEDIUM: unix: implement support for Linux abstract namespace sockets
These sockets are the same as Unix sockets except that there's no need
for any filesystem access. The address may be whatever string both sides
agree upon. This can be really convenient for inter-process communications
as well as for chaining backends to frontends.
These addresses are forced by prepending their address with "abns@" for
"abstract namespace".
diff --git a/src/standard.c b/src/standard.c
index 305c09e..9cec295 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -635,6 +635,11 @@
* - "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 '/'
+ * - 'abns@' -> force address to belong to the abstract namespace (Linux
+ * only). These sockets are just like Unix sockets but without
+ * the need for an underlying file system. The address is a
+ * string. Technically it's like a Unix socket with a zero in
+ * the first byte of the address.
* - "fd@" => an integer must follow, and is a file descriptor number.
*
* Also note that in order to avoid any ambiguity with IPv6 addresses, the ':'
@@ -655,6 +660,7 @@
char *back, *str2;
char *port1, *port2;
int portl, porth, porta;
+ int abstract = 0;
portl = porth = porta = 0;
@@ -668,8 +674,14 @@
if (strncmp(str2, "unix@", 5) == 0) {
str2 += 5;
+ abstract = 0;
ss.ss_family = AF_UNIX;
}
+ else if (strncmp(str2, "abns@", 5) == 0) {
+ str2 += 5;
+ abstract = 1;
+ ss.ss_family = AF_UNIX;
+ }
else if (strncmp(str2, "ipv4@", 5) == 0) {
str2 += 5;
ss.ss_family = AF_INET;
@@ -706,7 +718,7 @@
/* complete unix socket path name during startup or soft-restart is
* <unix_bind_prefix><path>.<pid>.<bak|tmp>
*/
- prefix_path_len = pfx ? strlen(pfx) : 0;
+ prefix_path_len = (pfx && !abstract) ? strlen(pfx) : 0;
max_path_len = (sizeof(((struct sockaddr_un *)&ss)->sun_path) - 1) -
(prefix_path_len ? prefix_path_len + 1 + 5 + 1 + 3 : 0);
@@ -716,9 +728,11 @@
goto out;
}
+ /* when abstract==1, we skip the first zero and copy all bytes except the trailing zero */
+ memset(((struct sockaddr_un *)&ss)->sun_path, 0, sizeof(((struct sockaddr_un *)&ss)->sun_path));
if (prefix_path_len)
memcpy(((struct sockaddr_un *)&ss)->sun_path, pfx, prefix_path_len);
- memcpy(((struct sockaddr_un *)&ss)->sun_path + prefix_path_len, str2, adr_len + 1);
+ memcpy(((struct sockaddr_un *)&ss)->sun_path + prefix_path_len + abstract, str2, adr_len + 1 - abstract);
}
else { /* IPv4 and IPv6 */
port1 = strrchr(str2, ':');