From 3a7e03aaff478b8e6b14d8a90fae8f78452d20e2 Mon Sep 17 00:00:00 2001
From: Joel Cunningham <joel.cunningham@me.com>
Date: Thu, 9 Feb 2017 22:32:29 -0600
Subject: [PATCH] Add errno support to if_indextoname()

This commit adds support in if_indextoname() to return ENXIO when
no interface is found.  This conforms to the Open Group/RFC 3493
specification

In order to leverage errno set support, the set_errno macro from
sockets.c was moved to sockets_priv.h
---
 src/api/if_api.c                     | 16 ++++++++--------
 src/api/sockets.c                    |  8 --------
 src/include/lwip/priv/sockets_priv.h |  8 ++++++++
 3 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/src/api/if_api.c b/src/api/if_api.c
index 6283b4a2..e1730ae9 100644
--- a/src/api/if_api.c
+++ b/src/api/if_api.c
@@ -43,8 +43,10 @@
 
 #if LWIP_SOCKET
 
+#include "lwip/errno.h"
 #include "lwip/if_api.h"
 #include "lwip/netifapi.h"
+#include "lwip/priv/sockets_priv.h"
 
 /**
  * @ingroup if_api
@@ -59,19 +61,17 @@ char *
 lwip_if_indextoname(unsigned int ifindex, char *ifname)
 {
 #if LWIP_NETIF_API
-  err_t err;
-  if (ifindex > 0xff) {
-    return NULL;
-  }
-  
-  err = netifapi_netif_index_to_name((u8_t)ifindex, ifname);
-  if (!err && ifname[0] != '\0') {
-    return ifname;
+  if (ifindex <= 0xff) {
+    err_t err = netifapi_netif_index_to_name((u8_t)ifindex, ifname);
+    if (!err && ifname[0] != '\0') {
+      return ifname;
+    }
   }
 #else /* LWIP_NETIF_API */
   LWIP_UNUSED_ARG(ifindex);
   LWIP_UNUSED_ARG(ifname);
 #endif /* LWIP_NETIF_API */
+  set_errno(ENXIO);
   return NULL;
 }
 
diff --git a/src/api/sockets.c b/src/api/sockets.c
index 25da2280..12aa6803 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -293,14 +293,6 @@ static struct lwip_select_cb *select_cb_list;
     and checked in event_callback to see if it has changed. */
 static volatile int select_cb_ctr;
 
-#if LWIP_SOCKET_SET_ERRNO
-#ifndef set_errno
-#define set_errno(err) do { if (err) { errno = (err); } } while(0)
-#endif
-#else /* LWIP_SOCKET_SET_ERRNO */
-#define set_errno(err)
-#endif /* LWIP_SOCKET_SET_ERRNO */
-
 #define sock_set_errno(sk, e) do { \
   const int sockerr = (e); \
   sk->err = (u8_t)sockerr; \
diff --git a/src/include/lwip/priv/sockets_priv.h b/src/include/lwip/priv/sockets_priv.h
index d45030a5..417a51b4 100644
--- a/src/include/lwip/priv/sockets_priv.h
+++ b/src/include/lwip/priv/sockets_priv.h
@@ -48,6 +48,14 @@
 extern "C" {
 #endif
 
+#if LWIP_SOCKET_SET_ERRNO
+#ifndef set_errno
+#define set_errno(err) do { if (err) { errno = (err); } } while(0)
+#endif
+#else /* LWIP_SOCKET_SET_ERRNO */
+#define set_errno(err)
+#endif /* LWIP_SOCKET_SET_ERRNO */
+
 #if !LWIP_TCPIP_CORE_LOCKING
 /** Maximum optlen used by setsockopt/getsockopt */
 #define LWIP_SETGETSOCKOPT_MAXOPTLEN 16