nss: getent: Print IPv6 scope ID for ahosts/ahostsv6 if available

This information is sometimes useful and actually required for
link-local addresses.

2 files changed, 32 insertions, 8 deletions

diff --git a/ChangeLog b/ChangeLog
index 46c219839b..77b4587196 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2019-02-12  Florian Weimer  <fweimer@redhat.com>
+
+	* nss/getent.c (ahosts_keys_int): Include IPv6 scope ID in output.
+
 2019-02-12  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
 	[BZ #24122]
diff --git a/nss/getent.c b/nss/getent.c
index f25de8f1fc..07a7d09795 100644
--- a/nss/getent.c
+++ b/nss/getent.c
@@ -40,6 +40,7 @@
 #include <netinet/in.h>
 #include <sys/socket.h>
 #include <scratch_buffer.h>
+#include <inttypes.h>
 
 /* Get libc version number.  */
 #include <version.h>
@@ -393,15 +394,34 @@ ahosts_keys_int (int af, int xflags, int number, char *key[])
 		  sockstr = sockbuf;
 		}
 
+	      /* Three digits per byte, plus '%' and null terminator.  */
+	      char scope[3 * sizeof (uint32_t) + 2];
+	      struct sockaddr_in6 *addr6
+		= (struct sockaddr_in6 *) runp->ai_addr;
+	      if (runp->ai_family != AF_INET6 || addr6->sin6_scope_id == 0)
+		/* No scope ID present.  */
+		scope[0] = '\0';
+	      else
+		snprintf (scope, sizeof (scope), "%%%" PRIu32,
+			  addr6->sin6_scope_id);
+
 	      char buf[INET6_ADDRSTRLEN];
-	      printf ("%-15s %-6s %s\n",
-		      inet_ntop (runp->ai_family,
-				 runp->ai_family == AF_INET
-				 ? (void *) &((struct sockaddr_in *) runp->ai_addr)->sin_addr
-				 : (void *) &((struct sockaddr_in6 *) runp->ai_addr)->sin6_addr,
-				 buf, sizeof (buf)),
-		      sockstr,
-		      runp->ai_canonname ?: "");
+	      if (inet_ntop (runp->ai_family,
+			     runp->ai_family == AF_INET
+			     ? (void *) &((struct sockaddr_in *) runp->ai_addr)->sin_addr
+			     : &addr6->sin6_addr,
+			     buf, sizeof (buf)) == NULL)
+		{
+		  strcpy (buf, "<invalid>");
+		  scope[0] = '\0';
+		}
+
+	      int pad = 15 - strlen (buf) - strlen (scope);
+	      if (pad < 0)
+		pad = 0;
+
+	      printf ("%s%-*s %-6s %s\n",
+		      buf, pad, scope, sockstr, runp->ai_canonname ?: "");
 
 	      runp = runp->ai_next;
 	    }