-static FILE *fopenmask(const char *filename, const char *mode, mode_t perms) {
- mode_t mask = umask(0);
- perms &= ~mask;
- umask(~perms);
- FILE *f = fopen(filename, mode);
-#ifdef HAVE_FCHMOD
- if((perms & 0444) && f)
- fchmod(fileno(f), perms);
-#endif
- umask(mask);
- return f;
+
+static bool try_bind(int port) {
+ struct addrinfo *ai = NULL;
+ struct addrinfo hint = {
+ .ai_flags = AI_PASSIVE,
+ .ai_family = AF_UNSPEC,
+ .ai_socktype = SOCK_STREAM,
+ .ai_protocol = IPPROTO_TCP,
+ };
+
+ char portstr[16];
+ snprintf(portstr, sizeof portstr, "%d", port);
+
+ if(getaddrinfo(NULL, portstr, &hint, &ai) || !ai)
+ return false;
+
+ while(ai) {
+ int fd = socket(ai->ai_family, SOCK_STREAM, IPPROTO_TCP);
+ if(!fd) {
+ freeaddrinfo(ai);
+ return false;
+ }
+ int result = bind(fd, ai->ai_addr, ai->ai_addrlen);
+ closesocket(fd);
+ if(result) {
+ freeaddrinfo(ai);
+ return false;
+ }
+ ai = ai->ai_next;
+ }
+
+ freeaddrinfo(ai);
+ return true;
+}
+
+static int check_port(meshlink_handle_t *mesh) {
+ if(try_bind(655))
+ return 655;
+
+ fprintf(stderr, "Warning: could not bind to port 655.\n");
+
+ for(int i = 0; i < 100; i++) {
+ int port = 0x1000 + (rand() & 0x7fff);
+ if(try_bind(port)) {
+ char filename[PATH_MAX];
+ snprintf(filename, sizeof filename, "%s" SLASH "hosts" SLASH "%s", mesh->confbase, mesh->name);
+ FILE *f = fopen(filename, "a");
+ if(!f) {
+ fprintf(stderr, "Please change MeshLink's Port manually.\n");
+ return 0;
+ }
+
+ fprintf(f, "Port = %d\n", port);
+ fclose(f);
+ fprintf(stderr, "MeshLink will instead listen on port %d.\n", port);
+ return port;
+ }
+ }
+
+ fprintf(stderr, "Please change MeshLink's Port manually.\n");
+ return 0;