Re: [PATCH] Add reentrant gethostbyname call

[Ian Holsman]

Justin Erenkrantz wrote:

During some testing with flood (~30 threads), we ran into a stack
corruption error in our code.  We tracked it down to the fact that we
were using a non-reentrant version of gethostbyname.  This patch lets
us call the reentrant version of gethostbyname and now we haven't
been able to recreate the segfault.

The only possible optimization would be the size of the temporary
buffer (currently 256). Roy mentioned that the address array in hostent has a maximum of 10 entries. If so, the size of the structure plus the maximum size of the array (10 entries) may be sufficient. If we send in a too small buffer, we should receive ERANGE.

Is there a reason why we shouldn't just use the re-entrant versions
where it is available?

also you can't use APR_HAS_THREADS to check,
as someone could have threads turned on in BSD, which
doesnt have a gethostbyname_r function
(at least acording to cvs.apache.org's man pages)

..Ian

Any reason we shouldn't commit?  -- justin

Index: network_io/unix/sa_common.c
===================================================================
RCS file: /home/cvs/apr/network_io/unix/sa_common.c,v
retrieving revision 1.34
diff -u -r1.34 sa_common.c
--- network_io/unix/sa_common.c 2001/05/02 02:54:11     1.34
+++ network_io/unix/sa_common.c 2001/07/20 02:29:30
@@ -380,6 +380,11 @@
        struct hostent *hp;
        apr_sockaddr_t *cursa;
        int curaddr;
+#if APR_HAS_THREADS
+        char tmp[256];
+        int hosterror;
+        struct hostent hs;
+#endif

        if (family == APR_UNSPEC) {
            family = APR_INET; /* we don't support IPv6 here */
@@ -395,11 +400,17 @@
        }
        else {
#endif
+#if APR_HAS_THREADS
+        hp = gethostbyname_r(hostname, &hs, tmp, 255, &hosterror);
+#else
        hp = gethostbyname(hostname);
+#endif

        if (!hp)  {
#ifdef WIN32
            apr_get_netos_error();
+#elif APR_HAS_THREADS
+            return (hosterror + APR_OS_START_SYSERR);
#else
            return (h_errno + APR_OS_START_SYSERR);
#endif