[libvirt] [PATCH] syntax-check: prohibit all new uses of gethostby* functions

[Jim Meyering]

"Daniel P. Berrange" <berrange at redhat.com> wrote:
> On Wed, Dec 10, 2008 at 07:33:17PM -0800, David Lutterkort wrote:
>> The attached patch makes virConnectGetHostname try a little harder to get a
>> FQDN on systems where gethostname only returns a short name without a
>> domain (which is pretty useless). The behavior is equivalent to 'hostname
>> --fqdn'.
>>
>> > From 2ae57d0c8c68c453b3f9715fcc9f83af0ebe84a0 Mon Sep 17 00:00:00 2001
>> From: David Lutterkort <lutter at redhat.com>
>> Date: Wed, 10 Dec 2008 18:34:39 -0800
>> Subject: [PATCH] virConnectGetHostname: return a fully qualified hostname
>>
>> Instead of doing the equivalent of 'hostname', do 'hostname --fqdn',
>> i.e. try to qualify the local host name by an additional call to
>> gethostbyname(3)
>> +
>> +char *virGetHostname(void)
>> +{
>> +    int r;
>> +    char hostname[HOST_NAME_MAX+1], *str;
>> +    struct hostent *he;
>> +
>> +    r = gethostname (hostname, HOST_NAME_MAX+1);
>> +    if (r == -1)
>> +        return NULL;
>> +    if (!(he = gethostbyname(hostname)))
>> +        return NULL;
>
> Actually, gethostbyname should never be used in any modern code as it is
> not thread safe. Instead use getaddrinfo() and  the AI_CANONNAME flag

Good point.
Yet another reason not to use gethostbyname.
I think it's time to make the prohibition official.
Here's a patch to do that:

>From 5105125b7a91d701ce2dc9f549814a8fa4e352d7 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering at redhat.com>
Date: Thu, 11 Dec 2008 11:49:40 +0100
Subject: [PATCH] syntax-check: prohibit all new uses of gethostby* functions

* Makefile.maint (sc_prohibit_gethostby): New rule.
* .x-sc_prohibit_gethostby: Exempt the few existing uses.
---
 .x-sc_prohibit_gethostby |    3 +++
 Makefile.maint           |    6 ++++++
 2 files changed, 9 insertions(+), 0 deletions(-)
 create mode 100644 .x-sc_prohibit_gethostby

diff --git a/.x-sc_prohibit_gethostby b/.x-sc_prohibit_gethostby
new file mode 100644
index 0000000..d74ea40
--- /dev/null
+++ b/.x-sc_prohibit_gethostby
@@ -0,0 +1,3 @@
+gnulib/lib/getaddrinfo.c
+gnulib/m4/getaddrinfo.m4
+src/xend_internal.c
diff --git a/Makefile.maint b/Makefile.maint
index 10d481b..051e4c0 100644
--- a/Makefile.maint
+++ b/Makefile.maint
@@ -390,6 +390,12 @@ sc_prohibit_virBufferAdd_with_string_literal:
 	  { echo '$(ME): use virBufferAddLit, not virBufferAdd,' \
 	      'with a string literal' 1>&2; exit 1; } || :

+# Not only do they fail to deal well with ipv6, but the gethostby*
+# functions are also not thread-safe.
+sc_prohibit_gethostby:
+	@grep -nE '\<gethostby(addr|name2?) *\(' $$($(VC_LIST_EXCEPT)) && \
+	  { echo '$(ME): use getaddrinfo, not gethostby*' 1>&2; exit 1; } || :
+
 # Avoid useless parentheses like those in this example:
 # #if defined (SYMBOL) || defined (SYM2)
 sc_useless_cpp_parens:
--
1.6.0.4.1044.g77718