CURLOPT_ADDRESS_SCOPE: fix range check and more

Commit 9081014 fixed most of the confusing issues between scope id and
scope however 844896d added bad limits checking assuming that the scope
is being set and not the scope id.

I have fixed the documentation so it all refers to scope ids.

In addition Curl_if2ip refered to the scope id as remote_scope_id which
is incorrect, so I renamed it to local_scope_id.

Adjusted-by: Daniel Stenberg

Closes #3655
Closes #3765
Fixes #3713

3 files changed, 19 insertions, 16 deletions

diff --git a/lib/if2ip.c b/lib/if2ip.c
index 6e27685a0..d003de678 100644
--- a/lib/if2ip.c
+++ b/lib/if2ip.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -97,7 +97,7 @@ unsigned int Curl_ipv6_scope(const struct sockaddr *sa)
 #if defined(HAVE_GETIFADDRS)
 
 if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
-                          unsigned int remote_scope_id, const char *interf,
+                          unsigned int local_scope_id, const char *interf,
                           char *buf, int buf_size)
 {
   struct ifaddrs *iface, *head;
@@ -109,7 +109,7 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
 
 #if !defined(HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID) || \
     !defined(ENABLE_IPV6)
-  (void) remote_scope_id;
+  (void) local_scope_id;
 #endif
 
   if(getifaddrs(&head) >= 0) {
@@ -145,7 +145,7 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
                             ->sin6_scope_id;
 
               /* If given, scope id should match. */
-              if(remote_scope_id && scopeid != remote_scope_id) {
+              if(local_scope_id && scopeid != local_scope_id) {
                 if(res == IF2IP_NOT_FOUND)
                   res = IF2IP_AF_NOT_SUPPORTED;
 
@@ -182,7 +182,7 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
 #elif defined(HAVE_IOCTL_SIOCGIFADDR)
 
 if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
-                          unsigned int remote_scope_id, const char *interf,
+                          unsigned int local_scope_id, const char *interf,
                           char *buf, int buf_size)
 {
   struct ifreq req;
@@ -192,7 +192,7 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
   size_t len;
 
   (void)remote_scope;
-  (void)remote_scope_id;
+  (void)local_scope_id;
 
   if(!interf || (af != AF_INET))
     return IF2IP_NOT_FOUND;
@@ -228,12 +228,12 @@ if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
 #else
 
 if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
-                          unsigned int remote_scope_id, const char *interf,
+                          unsigned int local_scope_id, const char *interf,
                           char *buf, int buf_size)
 {
     (void) af;
     (void) remote_scope;
-    (void) remote_scope_id;
+    (void) local_scope_id;
     (void) interf;
     (void) buf;
     (void) buf_size;
diff --git a/lib/if2ip.h b/lib/if2ip.h
index a11b1c222..f193d4257 100644
--- a/lib/if2ip.h
+++ b/lib/if2ip.h
@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -39,7 +39,7 @@ typedef enum {
 } if2ip_result_t;
 
 if2ip_result_t Curl_if2ip(int af, unsigned int remote_scope,
-                          unsigned int remote_scope_id, const char *interf,
+                          unsigned int local_scope_id, const char *interf,
                           char *buf, int buf_size);
 
 #ifdef __INTERIX
diff --git a/lib/setopt.c b/lib/setopt.c
index 6e596fa66..1df38fbb4 100644
--- a/lib/setopt.c
+++ b/lib/setopt.c
@@ -118,6 +118,7 @@ static CURLcode vsetopt(struct Curl_easy *data, CURLoption option,
   char *argptr;
   CURLcode result = CURLE_OK;
   long arg;
+  unsigned long uarg;
   curl_off_t bigsize;
 
   switch(option) {
@@ -2297,14 +2298,16 @@ static CURLcode vsetopt(struct Curl_easy *data, CURLoption option,
 
   case CURLOPT_ADDRESS_SCOPE:
     /*
-     * We always get longs when passed plain numericals, but for this value we
-     * know that an unsigned int will always hold the value so we blindly
-     * typecast to this type
+     * Use this scope id when using IPv6
+     * We always get longs when passed plain numericals so we should check
+     * that the value fits into an unsigned 32 bit integer.
      */
-    arg = va_arg(param, long);
-    if((arg < 0) || (arg > 0xf))
+    uarg = va_arg(param, unsigned long);
+#if SIZEOF_LONG > 4
+    if(uarg > UINT_MAX)
       return CURLE_BAD_FUNCTION_ARGUMENT;
-    data->set.scope_id = curlx_sltoui(arg);
+#endif
+    data->set.scope_id = (unsigned int)uarg;
     break;
 
   case CURLOPT_PROTOCOLS: