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Mon, 22 Jun 2020 13:08:54 +0000 (UTC) Subject: Re: [PATCH] qga: Use gethostname() instead of g_get_host_name() To: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org References: <8e73f685e10c684eb5e2c88c2185504d26f024fc.1592296355.git.mprivozn@redhat.com> <7e31a988-7d6f-7bc5-3563-e77efff87ca3@redhat.com> From: Michal Privoznik Message-ID: <1708cb61-0dbf-0537-28dd-cd82c8b30378@redhat.com> Date: Mon, 22 Jun 2020 15:08:53 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <7e31a988-7d6f-7bc5-3563-e77efff87ca3@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=mprivozn@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/22 02:57:26 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Richard Henderson , vfeenstr@redhat.com, mdroth@linux.vnet.ibm.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/22/20 12:14 PM, Philippe Mathieu-Daudé wrote: > Hi Michal, > > On 6/16/20 10:34 AM, Michal Privoznik wrote: >> Problem with g_get_host_name() is that on the first call it saves >> the hostname into a global variable and from then on, every >> subsequent call returns the saved hostname. Even if the hostname >> changes. This doesn't play nicely with guest agent, because if >> the hostname is acquired before the guest is set up (e.g. on the >> first boot, or before DHCP) we will report old, invalid hostname. >> >> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1845127 >> >> Signed-off-by: Michal Privoznik >> --- >> qga/commands.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++---- >> 1 file changed, 52 insertions(+), 4 deletions(-) >> >> diff --git a/qga/commands.c b/qga/commands.c >> index efc8b90281..ce3c2041a6 100644 >> --- a/qga/commands.c >> +++ b/qga/commands.c >> @@ -512,14 +512,62 @@ int ga_parse_whence(GuestFileWhence *whence, Error **errp) >> return -1; >> } >> >> +#ifndef HOST_NAME_MAX >> +# ifdef _POSIX_HOST_NAME_MAX >> +# define HOST_NAME_MAX _POSIX_HOST_NAME_MAX >> +# else >> +# define HOST_NAME_MAX 255 >> +# endif >> +#endif >> + >> GuestHostName *qmp_guest_get_host_name(Error **errp) >> { >> GuestHostName *result = NULL; >> - gchar const *hostname = g_get_host_name(); >> - if (hostname != NULL) { >> - result = g_new0(GuestHostName, 1); >> - result->host_name = g_strdup(hostname); >> + g_autofree char *hostname = NULL; >> + >> + /* >> + * We want to avoid using g_get_host_name() because that >> + * caches the result and we wouldn't reflect changes in the >> + * host name. >> + */ > > I see there is only one g_get_host_name() call in the > codebase, but can we have a generic qemu_get_host_name() > helper implemented in util/oslib-*c instead? Sure. Let me post a v2 so that I can include Richard's suggestion too. Michal