+
+int free_and_strdup(char **p, const char *s) {
+ char *t;
+
+ assert(p);
+
+ /* Replaces a string pointer with an strdup()ed new string,
+ * possibly freeing the old one. */
+
+ if (s) {
+ t = strdup(s);
+ if (!t)
+ return -ENOMEM;
+ } else
+ t = NULL;
+
+ free(*p);
+ *p = t;
+
+ return 0;
+}
+
+int sethostname_idempotent(const char *s) {
+ int r;
+ char buf[HOST_NAME_MAX + 1] = {};
+
+ assert(s);
+
+ r = gethostname(buf, sizeof(buf));
+ if (r < 0)
+ return -errno;
+
+ if (streq(buf, s))
+ return 0;
+
+ r = sethostname(s, strlen(s));
+ if (r < 0)
+ return -errno;
+
+ return 1;
+}
+
+int ptsname_malloc(int fd, char **ret) {
+ size_t l = 100;
+
+ assert(fd >= 0);
+ assert(ret);
+
+ for (;;) {
+ char *c;
+
+ c = new(char, l);
+ if (!c)
+ return -ENOMEM;
+
+ if (ptsname_r(fd, c, l) == 0) {
+ *ret = c;
+ return 0;
+ }
+ if (errno != ERANGE) {
+ free(c);
+ return -errno;
+ }
+
+ free(c);
+ l *= 2;
+ }
+}
+
+int openpt_in_namespace(pid_t pid, int flags) {
+ _cleanup_close_ int pidnsfd = -1, mntnsfd = -1, rootfd = -1;
+ _cleanup_close_pair_ int pair[2] = { -1, -1 };
+ union {
+ struct cmsghdr cmsghdr;
+ uint8_t buf[CMSG_SPACE(sizeof(int))];
+ } control = {};
+ struct msghdr mh = {
+ .msg_control = &control,
+ .msg_controllen = sizeof(control),
+ };
+ struct cmsghdr *cmsg;
+ siginfo_t si;
+ pid_t child;
+ int r;
+
+ assert(pid > 0);
+
+ r = namespace_open(pid, &pidnsfd, &mntnsfd, NULL, &rootfd);
+ if (r < 0)
+ return r;
+
+ if (socketpair(AF_UNIX, SOCK_DGRAM, 0, pair) < 0)
+ return -errno;
+
+ child = fork();
+ if (child < 0)
+ return -errno;
+
+ if (child == 0) {
+ int master;
+
+ pair[0] = safe_close(pair[0]);
+
+ r = namespace_enter(pidnsfd, mntnsfd, -1, rootfd);
+ if (r < 0)
+ _exit(EXIT_FAILURE);
+
+ master = posix_openpt(flags);
+ if (master < 0)
+ _exit(EXIT_FAILURE);
+
+ cmsg = CMSG_FIRSTHDR(&mh);
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+ memcpy(CMSG_DATA(cmsg), &master, sizeof(int));
+
+ mh.msg_controllen = cmsg->cmsg_len;
+
+ if (sendmsg(pair[1], &mh, MSG_NOSIGNAL) < 0)
+ _exit(EXIT_FAILURE);
+
+ _exit(EXIT_SUCCESS);
+ }
+
+ pair[1] = safe_close(pair[1]);
+
+ r = wait_for_terminate(child, &si);
+ if (r < 0)
+ return r;
+ if (si.si_code != CLD_EXITED || si.si_status != EXIT_SUCCESS)
+ return -EIO;
+
+ if (recvmsg(pair[0], &mh, MSG_NOSIGNAL|MSG_CMSG_CLOEXEC) < 0)
+ return -errno;
+
+ for (cmsg = CMSG_FIRSTHDR(&mh); cmsg; cmsg = CMSG_NXTHDR(&mh, cmsg))
+ if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
+ int *fds;
+ unsigned n_fds;
+
+ fds = (int*) CMSG_DATA(cmsg);
+ n_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
+
+ if (n_fds != 1) {
+ close_many(fds, n_fds);
+ return -EIO;
+ }
+
+ return fds[0];
+ }
+
+ return -EIO;
+}