+static int instance_from_socket(int fd, unsigned nr, char **instance) {
+ socklen_t l;
+ char *r;
+ union {
+ struct sockaddr sa;
+ struct sockaddr_un un;
+ struct sockaddr_in in;
+ struct sockaddr_in6 in6;
+ struct sockaddr_storage storage;
+ } local, remote;
+
+ assert(fd >= 0);
+ assert(instance);
+
+ l = sizeof(local);
+ if (getsockname(fd, &local.sa, &l) < 0)
+ return -errno;
+
+ l = sizeof(remote);
+ if (getpeername(fd, &remote.sa, &l) < 0)
+ return -errno;
+
+ switch (local.sa.sa_family) {
+
+ case AF_INET: {
+ uint32_t
+ a = ntohl(local.in.sin_addr.s_addr),
+ b = ntohl(remote.in.sin_addr.s_addr);
+
+ if (asprintf(&r,
+ "%u-%u.%u.%u.%u-%u-%u.%u.%u.%u-%u",
+ nr,
+ a >> 24, (a >> 16) & 0xFF, (a >> 8) & 0xFF, a & 0xFF,
+ ntohs(local.in.sin_port),
+ b >> 24, (b >> 16) & 0xFF, (b >> 8) & 0xFF, b & 0xFF,
+ ntohs(remote.in.sin_port)) < 0)
+ return -ENOMEM;
+
+ break;
+ }
+
+ case AF_INET6: {
+ char a[INET6_ADDRSTRLEN], b[INET6_ADDRSTRLEN];
+
+ if (asprintf(&r,
+ "%u-%s-%u-%s-%u",
+ nr,
+ inet_ntop(AF_INET6, &local.in6.sin6_addr, a, sizeof(a)),
+ ntohs(local.in6.sin6_port),
+ inet_ntop(AF_INET6, &remote.in6.sin6_addr, b, sizeof(b)),
+ ntohs(remote.in6.sin6_port)) < 0)
+ return -ENOMEM;
+
+ break;
+ }
+
+ case AF_UNIX: {
+ struct ucred ucred;
+
+ l = sizeof(ucred);
+ if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &l) < 0)
+ return -errno;
+
+ if (asprintf(&r,
+ "%u-%llu-%llu",
+ nr,
+ (unsigned long long) ucred.pid,
+ (unsigned long long) ucred.uid) < 0)
+ return -ENOMEM;
+
+ break;
+ }
+
+ default:
+ assert_not_reached("Unhandled socket type.");
+ }
+
+ *instance = r;
+ return 0;
+}
+