dirmngr: Add workaround for broken getaddrinfo.

* dirmngr/dns-stuff.c (resolve_name_standard): On failure retry by
first resolving the CNAME.
(get_dns_cname): New.

* dirmngr/t-dns-stuff.c (main): Add option --cname.
--

At least the getaddrinfo implementation in glibc 2.19-13 from Debian
returns EAI_NONAME if the CNAME points to a too long list of A/AAAA
addresses.  Looking at the wire the data is correctly returned from
the server but getaddrinfo seems to get confused by truncation and
retry.  To fix this we resolve the CNAME again and call getaddrinfo
again with the canonical name.

Signed-off-by: Werner Koch <[email protected]>

1 files changed, 23 insertions, 0 deletions

diff --git a/dirmngr/t-dns-stuff.c b/dirmngr/t-dns-stuff.c
index f216d06eb..4ecbd64f0 100644
--- a/dirmngr/t-dns-stuff.c
+++ b/dirmngr/t-dns-stuff.c
@@ -44,6 +44,7 @@ main (int argc, char **argv)
   int opt_cert = 0;
   int opt_srv = 0;
   int opt_bracket = 0;
+  int opt_cname = 0;
   char const *name = NULL;
 
   gpgrt_init ();
@@ -68,6 +69,7 @@ main (int argc, char **argv)
                  "  --bracket         enclose v6 addresses in brackets\n"
                  "  --cert            lookup a CERT RR\n"
                  "  --srv             lookup a SRV RR\n"
+                 "  --cname           lookup a CNAME RR\n"
                  , stdout);
           exit (0);
         }
@@ -102,6 +104,11 @@ main (int argc, char **argv)
           any_options = opt_srv = 1;
           argc--; argv++;
         }
+      else if (!strcmp (*argv, "--cname"))
+        {
+          any_options = opt_cname = 1;
+          argc--; argv++;
+        }
       else if (!strncmp (*argv, "--", 2))
         {
           fprintf (stderr, PGM ": unknown option '%s'\n", *argv);
@@ -177,6 +184,22 @@ main (int argc, char **argv)
       xfree (fpr);
       xfree (url);
     }
+  else if (opt_cname)
+    {
+      char *cname;
+
+      printf ("CNAME lookup on '%s'\n", name);
+      err = get_dns_cname (name, &cname);
+      if (err)
+        printf ("get_dns_cname failed: %s <%s>\n",
+                gpg_strerror (err), gpg_strsource (err));
+      else
+        {
+          printf ("CNAME found: '%s'\n", cname);
+        }
+
+      xfree (cname);
+    }
   else if (opt_srv)
     {
       struct srventry *srv;