From 01c11e16b118353ffbb6be7f28cae41bf5d8e200 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Mon, 5 May 2025 08:01:52 -0700
Subject: [PATCH] add SockAddr::map6to4()

---
 src/osiSockExt.h  |  1 +
 src/util.cpp      | 17 +++++++++++++++++
 test/testsock.cpp | 16 +++++++++++++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/src/osiSockExt.h b/src/osiSockExt.h
index 4b8a615..e2f3ad7 100644
--- a/src/osiSockExt.h
+++ b/src/osiSockExt.h
@@ -78,6 +78,7 @@ public:
     bool isMCast() const noexcept;
 
     SockAddr map4to6() const;
+    SockAddr map6to4() const;
 
     store_t* operator->() { return &store; }
     const store_t* operator->() const { return &store; }
diff --git a/src/util.cpp b/src/util.cpp
index 6b7708b..794ee29 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -601,6 +601,23 @@ SockAddr SockAddr::map4to6() const
     return ret;
 }
 
+SockAddr SockAddr::map6to4() const
+{
+    constexpr uint8_t is4[12] = {0,0,0,0, 0,0,0,0, 0,0,0xff,0xff};
+    SockAddr ret;
+    if(family()==AF_INET6 && memcmp(store.in6.sin6_addr.s6_addr, is4, 12)==0) {
+        ret->in.sin_family = AF_INET;
+        memcpy(&ret->in.sin_addr.s_addr,
+               &store.in6.sin6_addr.s6_addr[12],
+                4);
+        ret->in.sin_port = store.in6.sin6_port;
+
+    } else {
+        ret = *this;
+    }
+    return ret;
+}
+
 std::string SockAddr::tostring() const
 {
     std::ostringstream strm;
diff --git a/test/testsock.cpp b/test/testsock.cpp
index dde60b3..bc1e3a1 100644
--- a/test/testsock.cpp
+++ b/test/testsock.cpp
@@ -90,6 +90,20 @@ void testEndPoint()
         testEq(ep.iface, "ifname");
         testEq(ep.ttl, 1);
     }
+    {
+        SockEndpoint ep("[::ffff:192.168.1.1]");
+        testEq(ep.addr.tostring(), "[::ffff:192.168.1.1]");
+        testEq(ep.addr.map6to4().tostring(), "192.168.1.1");
+        testEq(ep.iface, "");
+        testEq(ep.ttl, -1);
+    }
+    {
+        SockEndpoint ep("[1234::1]");
+        testEq(ep.addr.tostring(), "[1234::1]");
+        testEq(ep.addr.map6to4().tostring(), "[1234::1]");
+        testEq(ep.iface, "");
+        testEq(ep.ttl, -1);
+    }
 
     std::vector<std::string> bad({
         "127.0.0.",
@@ -542,7 +556,7 @@ MAIN(testsock)
 {
     SockAttach attach;
     logger_config_env();
-    testPlan(101);
+    testPlan(109);
     testSetup();
     testStackID();
     testEndPoint();