Fix TCP send to IPv6 link local addresses (#7207)

credit: Simon Arlott @nomis - similar to #6541 for TCP (#7207)

Author: d-a-v

libraries/ESP8266WiFi/src/include/ClientContext.h

@@ -127,8 +127,14 @@ class ClientContext
         }
     }
 
-    int connect(CONST ip_addr_t* addr, uint16_t port)
+    int connect(ip_addr_t* addr, uint16_t port)
     {
+#if LWIP_IPV6
+        // Set zone so that link local addresses use the default interface
+        if (IP_IS_V6(addr) && ip6_addr_lacks_zone(ip_2_ip6(addr), IP6_UNKNOWN)) {
+            ip6_addr_assign_zone(ip_2_ip6(addr), IP6_UNKNOWN, netif_default);
+        }
+#endif
         err_t err = tcp_connect(_pcb, addr, port, &ClientContext::_s_connected);
         if (err != ERR_OK) {
             return 0;

libraries/ESP8266WiFi/src/include/UdpContext.h

@@ -117,7 +117,7 @@ class UdpContext
 #if LWIP_IPV6
         // Set zone so that link local addresses use the default interface
         if (IP_IS_V6(&_pcb->remote_ip) && ip6_addr_lacks_zone(ip_2_ip6(&_pcb->remote_ip), IP6_UNKNOWN)) {
-            ip6_addr_assign_zone(ip_2_ip6(&_pcb->remote_ip),IP6_UNKNOWN, netif_default);
+            ip6_addr_assign_zone(ip_2_ip6(&_pcb->remote_ip), IP6_UNKNOWN, netif_default);
         }
 #endif
         return true;