From 147cdce70b22ae7cee9fb4fe123db40952f31c9e Mon Sep 17 00:00:00 2001
From: David Zeuthen <zeuthen@chromium.org>
Date: Tue, 5 Mar 2013 11:52:38 -0800
Subject: [PATCH] avahi-daemon: add option "host-name-from-machine-id="

Signed-off-by: David Zeuthen <zeuthen@chromium.org>
---
 avahi-daemon/main.c            | 33 +++++++++++++++++++++++++++++++++
 man/avahi-daemon.conf.5.xml.in |  6 ++++++
 2 files changed, 39 insertions(+)

diff --git a/avahi-daemon/main.c b/avahi-daemon/main.c
index d46f40a..8c28fd6 100644
--- a/avahi-daemon/main.c
+++ b/avahi-daemon/main.c
@@ -65,6 +65,7 @@
 #include <avahi-core/publish.h>
 #include <avahi-core/dns-srv-rr.h>
 #include <avahi-core/log.h>
+#include <avahi-core/util.h>
 
 #ifdef ENABLE_CHROOT
 #include "chroot.h"
@@ -576,6 +577,29 @@ static int parse_usec(const char *s, AvahiUsec *u) {
     return 0;
 }
 
+static char *get_machine_id(void) {
+    int fd;
+    char buf[32];
+
+    fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+    if (fd == -1 && errno == ENOENT)
+        fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+    if (fd == -1)
+        return NULL;
+
+    /* File is on a filesystem so we never get EINTR or partial reads */
+    if (read(fd, buf, sizeof buf) != sizeof buf) {
+        close(fd);
+        return NULL;
+    }
+    close(fd);
+
+    /* Contents can be lower, upper and even mixed case so normalize */
+    avahi_strdown(buf);
+
+    return avahi_strndup(buf, sizeof buf);
+}
+
 static int load_config_file(DaemonConfig *c) {
     int r = -1;
     AvahiIniFile *f;
@@ -631,6 +655,15 @@ static int load_config_file(DaemonConfig *c) {
                     c->server_config.use_iff_running = is_yes(p->value);
                 else if (strcasecmp(p->key, "disallow-other-stacks") == 0)
                     c->server_config.disallow_other_stacks = is_yes(p->value);
+                else if (strcasecmp(p->key, "host-name-from-machine-id") == 0) {
+                    if (*(p->value) == 'y' || *(p->value) == 'Y') {
+                        char *machine_id = get_machine_id();
+                        if (machine_id != NULL) {
+                            avahi_free(c->server_config.host_name);
+                            c->server_config.host_name = machine_id;
+                        }
+                    }
+                }
 #ifdef HAVE_DBUS
                 else if (strcasecmp(p->key, "enable-dbus") == 0) {
 
diff --git a/man/avahi-daemon.conf.5.xml.in b/man/avahi-daemon.conf.5.xml.in
index bea7ed5..2d15017 100644
--- a/man/avahi-daemon.conf.5.xml.in
+++ b/man/avahi-daemon.conf.5.xml.in
@@ -39,6 +39,12 @@
       name as set with the sethostname() system call.</p>
     </option>
 
+    <option>
+      <p><opt>host-name-from-machine-id=</opt> Takes a boolean
+      value ("yes" or "no"). If set to "yes" avahi-daemon
+      will use the machine-id as name on the LAN.</p>
+    </option>
+
     <option>
       <p><opt>domain-name=</opt> Set the default domain name avahi-daemon
       tries to register its host name and services on the LAN in. If
-- 
2.39.5