From 1a9d7092d093700836945d2c7f5778c0f49c16d9 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Wed, 28 May 2014 18:35:10 +0100
Subject: [PATCH] scope if index to name conversion

---
 src/addrfam.c | 36 +++++++++++++++++++++++++++++++-----
 src/adns.h    |  7 ++++++-
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/src/addrfam.c b/src/addrfam.c
index 0f4a820..10cb1ce 100644
--- a/src/addrfam.c
+++ b/src/addrfam.c
@@ -30,6 +30,7 @@
 #include <unistd.h>
 #include <inttypes.h>
 #include <stddef.h>
+#include <stdbool.h>
 
 #include <sys/types.h>
 #include <netdb.h>
@@ -213,6 +214,14 @@ const void *adns__sockaddr_to_inaddr(const struct sockaddr *sa)
 # define af_debug(fmt,...) ((void)("" fmt "", __VA_ARGS__))
 #endif
 
+static bool addrtext_our_errno(int e) {
+  return
+    e==EAFNOSUPPORT ||
+    e==EINVAL ||
+    e==ENOSPC ||
+    e==ENOSYS;
+}
+
 int adns_text2addr(const char *addr, uint16_t port, struct sockaddr *sa,
 		   socklen_t *salen /* set if OK or ENOSPC */) {
   int af;
@@ -313,8 +322,7 @@ int adns_text2addr(const char *addr, uint16_t port, struct sockaddr *sa,
 		 strerror(errno));
 	if (errno==0) {
 	  return ENXIO;
-	} else if (errno==EAFNOSUPPORT || errno==EINVAL ||
-		   errno==ENOSPC || errno==ENOSYS) {
+	} else if (addrtext_our_errno(errno)) {
 	  /* we use these for other purposes, urgh. */
 	  perror("adns: adns_text2addr: if_nametoindex"
 		 " failed with unexpected error");
@@ -364,9 +372,27 @@ int adns_addr2text(const struct sockaddr *sa,
     if (scope) {
       int scopeoffset = strlen(addr_buffer);
       int remain = *addr_buflen - scopeoffset;
-      int r = snprintf(addr_buffer + scopeoffset, remain,
-		       "%%%"PRIu32"", scope);
-      assert(r < *addr_buflen - scopeoffset);
+      char *scopeptr =  addr_buffer + scopeoffset;
+      assert(remain >= IF_NAMESIZE+1/*%*/);
+      *scopeptr++= '%'; remain--;
+      char *ok = scope > UINT_MAX
+	? 0 /* we can't pass it to if_indextoname then */
+	: if_indextoname(scope, scopeptr);
+      if (!ok) {
+	if (errno==ENXIO) {
+	  /* fair enough, show it as a number then */
+	} else if (addrtext_our_errno(errno)) {
+	  /* we use these for other purposes, urgh. */
+	  perror("adns: adns_addr2text: if_indextoname"
+		 " failed with unexpected error");
+	  return EIO;
+	} else {
+	  return errno;
+	}
+	int r = snprintf(scopeptr, remain,
+			 "%"PRIu32"", scope);
+	assert(r < *addr_buflen - scopeoffset);
+      }
       af_debug("printed scoped address `%s'", addr_buffer);
     }
   }
diff --git a/src/adns.h b/src/adns.h
index bb88395..028d83c 100644
--- a/src/adns.h
+++ b/src/adns.h
@@ -66,6 +66,7 @@
 #include <netinet/in.h>
 #include <sys/time.h>
 #include <unistd.h>
+#include <net/if.h>
 
 #ifdef __cplusplus
 extern "C" { /* I really dislike this - iwj. */
@@ -682,7 +683,10 @@ void adns_finish(adns_state ads);
  * they will be cancelled.
  */
 
-#define ADNS_ADDR2TEXT_BUFLEN (INET6_ADDRSTRLEN +1/*%*/ +9/*uint32*/ +1/*nul*/)
+#define ADNS_ADDR2TEXT_BUFLEN					\
+  (INET6_ADDRSTRLEN + 1/*%*/					\
+  + ((IF_NAMESIZE-1) > 9 ? (IF_NAMESIZE-1) : 9/*uint32*/)	\
+  + 1/* nul; included in IF_NAMESIZE */)
 
 int adns_text2addr(const char *addr, uint16_t port, struct sockaddr *sa,
 		   socklen_t *salen /* set if OK or ENOSPC; otherwise undef */);
@@ -698,6 +702,7 @@ int adns_addr2text(const struct sockaddr *sa,
    *   ENOSYS       address is not link local
    *   ENXIO        if_nametoindex said it wasn't a valid name
    *   EIO          if_nametoindex went crazy (adns prints a message to stderr)
+   * Extra errors are possible from text2addr and addr2text with scopes:
    *   any other    if_nametoindex failed
    * port is always in host byte order and is simply copied to and
    * from the appropriate sockaddr field (byteswapped as necessary).
-- 
2.11.0