[systemd-commits] man/hostnamectl.xml src/hostname

[Lennart Poettering]

 man/hostnamectl.xml      |    8 +++-----
 src/hostname/hostnamed.c |   35 ++++++++++++++++++++++++++++++-----
 2 files changed, 33 insertions(+), 10 deletions(-)

New commits:
commit c779a44222161155c039a7fd2fd304c006590ac7
Author: Stef Walter <stef at thewalter.net>
Date:   Wed Feb 12 09:46:31 2014 +0100

    hostnamed: Fix the way that static and transient host names interact
    
    It is almost always incorrect to allow DHCP or other sources of
    transient host names to override an explicitly configured static host
    name.
    
    This commit changes things so that if a static host name is set, this
    will override the transient host name (eg: provided via DHCP). Transient
    host names can still be used to provide host names for machines that have
    not been explicitly configured with a static host name.
    
    The exception to this rule is if the static host name is set to
    "localhost". In those cases we act as if no
    static host name has been explicitly set.
    
    As discussed elsewhere, systemd may want to have an fd based ownership
    of the transient name. That part is not included in this commit.

diff --git a/man/hostnamectl.xml b/man/hostnamectl.xml
index 6746a70..a11f221 100644
--- a/man/hostnamectl.xml
+++ b/man/hostnamectl.xml
@@ -69,11 +69,9 @@
                 (e.g. "Lennart's Laptop"), the static hostname which
                 is used to initialize the kernel hostname at boot
                 (e.g. "lennarts-laptop"), and the transient hostname
-                which might be assigned temporarily due to network
-                configuration and might revert back to the static
-                hostname if network connectivity is lost and is only
-                temporarily written to the kernel hostname
-                (e.g. "dhcp-47-11").</para>
+                which is a default received from network configuration.
+                If a static hostname is set, and is valid (something other
+                than localhost) then the transient hostname is not used.</para>
 
                 <para>Note that the pretty hostname has little
                 restrictions on the characters used, while the static
diff --git a/src/hostname/hostnamed.c b/src/hostname/hostnamed.c
index 5c767cd..a350490 100644
--- a/src/hostname/hostnamed.c
+++ b/src/hostname/hostnamed.c
@@ -250,16 +250,35 @@ static char* context_fallback_icon_name(Context *c) {
         return strdup("computer");
 }
 
-static int context_write_data_hostname(Context *c) {
+static bool hostname_is_useful(const char *hn) {
+        return !isempty(hn) && !streq(hn, "localhost");
+}
+
+static int context_update_kernel_hostname(Context *c) {
+        const char *static_hn;
         const char *hn;
 
         assert(c);
 
-        if (isempty(c->data[PROP_HOSTNAME]))
-                hn = "localhost";
-        else
+        static_hn = c->data[PROP_STATIC_HOSTNAME];
+
+        /* /etc/hostname with something other than "localhost"
+         * has the highest preference ... */
+        if (hostname_is_useful(static_hn))
+                hn = static_hn;
+
+        /* ... the transient host name, (ie: DHCP) comes next ...*/
+        else if (!isempty(c->data[PROP_HOSTNAME]))
                 hn = c->data[PROP_HOSTNAME];
 
+        /* ... fallback to static "localhost.*" ignored above ... */
+        else if (!isempty(static_hn))
+                hn = static_hn;
+
+        /* ... and the ultimate fallback */
+        else
+                hn = "localhost";
+
         if (sethostname(hn, strlen(hn)) < 0)
                 return -errno;
 
@@ -411,7 +430,7 @@ static int method_set_hostname(sd_bus *bus, sd_bus_message *m, void *userdata, s
         free(c->data[PROP_HOSTNAME]);
         c->data[PROP_HOSTNAME] = h;
 
-        r = context_write_data_hostname(c);
+        r = context_update_kernel_hostname(c);
         if (r < 0) {
                 log_error("Failed to set host name: %s", strerror(-r));
                 return sd_bus_error_set_errnof(error, r, "Failed to set hostname: %s", strerror(-r));
@@ -463,6 +482,12 @@ static int method_set_static_hostname(sd_bus *bus, sd_bus_message *m, void *user
                 c->data[PROP_STATIC_HOSTNAME] = h;
         }
 
+        r = context_update_kernel_hostname(c);
+        if (r < 0) {
+                log_error("Failed to set host name: %s", strerror(-r));
+                return sd_bus_error_set_errnof(error, r, "Failed to set hostname: %s", strerror(-r));
+        }
+
         r = context_write_data_static_hostname(c);
         if (r < 0) {
                 log_error("Failed to write static host name: %s", strerror(-r));