From f51b1da9d5e8786e4eebdc6e217f047e5679485d Mon Sep 17 00:00:00 2001
From: Thomas Kolb <cfr34k-git@tkolb.de>
Date: Sun, 10 Nov 2024 21:39:15 +0100
Subject: [PATCH] connection: calculate IPv6 address for peer

---
 impl/src/layer2/connection.c | 21 +++++++++++++++++++++
 impl/src/layer2/connection.h |  4 ++++
 2 files changed, 25 insertions(+)

diff --git a/impl/src/layer2/connection.c b/impl/src/layer2/connection.c
index 069b444..cadd193 100644
--- a/impl/src/layer2/connection.c
+++ b/impl/src/layer2/connection.c
@@ -41,6 +41,27 @@ result_t connection_init(
 
 	ctx->user_context = user_ctx;
 
+	// calculate IPv6 address
+	struct in6_addr net_addr;
+	inet_pton(AF_INET6, IPV6_NET, &net_addr);
+
+	memset(ctx->peer_ipv6_addr.s6_addr, 0, sizeof(ctx->peer_ipv6_addr));
+	memcpy(ctx->peer_ipv6_addr.s6_addr, net_addr.s6_addr, 8); // copy the network part
+
+	// fill the host part from the peer’s ham64 address. The bytes are filled in
+	// reverse order to make the „readable“ IPv6 address as short as possible.
+	for(uint8_t i = 0; i < peer_addr->length; i++) {
+		ctx->peer_ipv6_addr.s6_addr[15 - 2*i] = (peer_addr->addr[i] >> 8) & 0xFF;
+		ctx->peer_ipv6_addr.s6_addr[14 - 2*i] = (peer_addr->addr[i] >> 0) & 0xFF;
+	}
+
+	// print the address for debugging
+	char ipv6_str[INET6_ADDRSTRLEN];
+	char ham64_str[HAM64_FMT_MAX_LEN];
+	ham64_format(peer_addr, ham64_str);
+	inet_ntop(AF_INET6, &ctx->peer_ipv6_addr, ipv6_str, sizeof(ipv6_str));
+	LOG(LVL_DEBUG, "IPv6 address assigned to %s is %s.", ham64_str, ipv6_str);
+
 	ctx->conn_state = CONN_STATE_INITIALIZED;
 
 	return OK;
diff --git a/impl/src/layer2/connection.h b/impl/src/layer2/connection.h
index 46979be..4e27370 100644
--- a/impl/src/layer2/connection.h
+++ b/impl/src/layer2/connection.h
@@ -14,6 +14,8 @@
 
 #include "packet_queue.h"
 
+#include <arpa/inet.h>
+
 struct connection_ctx_s;
 
 typedef enum {
@@ -44,6 +46,8 @@ typedef struct connection_ctx_s {
 	ham64_t my_addr;             //!< The local link layer address.
 	ham64_t peer_addr;           //!< The link layer address of the peer.
 
+	struct in6_addr peer_ipv6_addr;  //!< The peer’s IPv6 address (generated from LL address)
+
 	uint8_t last_acked_seq;      //!< Next sequence number expected by the peer (from last Ack).
 	uint8_t next_expected_seq;   //!< Next sequence number expected by us.