From 356c8008dd8c8c135bf8caeb250a6cb8cea5c36a Mon Sep 17 00:00:00 2001
From: Frank Engelhardt <frank.engelhardt@ovgu.de>
Date: Thu, 11 Jun 2020 16:22:26 +0200
Subject: [PATCH 1/2] posix_sockets: use sin6_scope_id field to specify netif

---
 sys/posix/sockets/posix_sockets.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sys/posix/sockets/posix_sockets.c b/sys/posix/sockets/posix_sockets.c
index f98cb233ad..5781e63899 100644
--- a/sys/posix/sockets/posix_sockets.c
+++ b/sys/posix/sockets/posix_sockets.c
@@ -238,6 +238,9 @@ static int _sockaddr_to_ep(const struct sockaddr *address, socklen_t address_len
             out->family = AF_INET6;
             memcpy(&out->addr.ipv6, &in6_addr->sin6_addr, sizeof(out->addr.ipv6));
             out->port = ntohs(in6_addr->sin6_port);
+            if (in6_addr->sin6_scope_id != 0) {
+                out->netif = (uint16_t) in6_addr->sin6_scope_id;
+            }
             break;
 #endif
         default:

From 76cdc1b4d87d1217c3a7138065cc24027d39000b Mon Sep 17 00:00:00 2001
From: Frank Engelhardt <frank.engelhardt@ovgu.de>
Date: Thu, 11 Jun 2020 16:24:29 +0200
Subject: [PATCH 2/2] examples/posix_sockets: parse ipv6 interface id

---
 examples/posix_sockets/udp.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/examples/posix_sockets/udp.c b/examples/posix_sockets/udp.c
index b49edf9fc6..72c5dff351 100644
--- a/examples/posix_sockets/udp.c
+++ b/examples/posix_sockets/udp.c
@@ -33,6 +33,11 @@
 #include <sys/socket.h>
 #include <unistd.h>
 
+#ifdef SOCK_HAS_IPV6
+#include "net/ipv6/addr.h"     /* for interface parsing */
+#include "net/netif.h"         /* for resolving ipv6 scope */
+#endif /* SOCK_HAS_IPV6 */
+
 #include "thread.h"
 
 #define SERVER_MSG_QUEUE_SIZE   (8)
@@ -98,6 +103,20 @@ static int udp_send(char *addr_str, char *port_str, char *data, unsigned int num
     src.sin6_family = AF_INET6;
     dst.sin6_family = AF_INET6;
     memset(&src.sin6_addr, 0, sizeof(src.sin6_addr));
+    /* parse interface id */
+#ifdef SOCK_HAS_IPV6
+    char *iface;
+    iface = ipv6_addr_split_iface(addr_str); /* also removes interface id */
+    if (iface) {
+        netif_t *netif = netif_get_by_name(iface);
+        if (netif) {
+            dst.sin6_scope_id = (uint32_t) netif_get_id(netif);
+        }
+        else {
+            printf("unknown network interface %s\n", iface);
+        }
+    }
+#endif /* SOCK_HAS_IPV6 */
     /* parse destination address */
     if (inet_pton(AF_INET6, addr_str, &dst.sin6_addr) != 1) {
         puts("Error: unable to parse destination address");