From 94cb32bc4624275e2dc5cd746f58ea202921208d Mon Sep 17 00:00:00 2001
From: Sofia Rodrigues <sofia@algebraic.dev>
Date: Tue, 21 Oct 2025 11:17:22 -0300
Subject: [PATCH] fix: ipv4 address encoding from libuv to lean (#10854)

This PR fixes the IPv4 address encoding from libuv to lean
---
 src/runtime/uv/dns.cpp        | 14 +++++++++++++-
 tests/lean/run/async_dns.lean | 26 ++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/src/runtime/uv/dns.cpp b/src/runtime/uv/dns.cpp
index e72c5077fc..e1cea0349a 100644
--- a/src/runtime/uv/dns.cpp
+++ b/src/runtime/uv/dns.cpp
@@ -81,7 +81,19 @@ extern "C" LEAN_EXPORT lean_obj_res lean_uv_dns_get_info(b_obj_arg name, b_obj_a
 
         for (struct addrinfo* ai = res; ai != NULL; ai = ai->ai_next) {
             const struct sockaddr* sin_addr = (const struct sockaddr*)ai->ai_addr;
-            in_addr_storage* storage_addr =  (in_addr_storage*)sin_addr->sa_data;
+
+            in_addr_storage* storage_addr;
+
+            if (sin_addr->sa_family == AF_INET) {
+                struct sockaddr_in* ipv4 = (struct sockaddr_in*)sin_addr;
+                storage_addr = (in_addr_storage*)&(ipv4->sin_addr);
+            } else if (sin_addr->sa_family == AF_INET6) {
+                struct sockaddr_in6* ipv6 = (struct sockaddr_in6*)sin_addr;
+                storage_addr = (in_addr_storage*)&(ipv6->sin6_addr);
+            } else {
+                continue;
+            }
+
             lean_object* addr = lean_in_addr_storage_to_ip_addr((short)sin_addr->sa_family, storage_addr);
             arr = lean_array_push(arr, addr);
         }
diff --git a/tests/lean/run/async_dns.lean b/tests/lean/run/async_dns.lean
index c6c5dbf617..997d531ec4 100644
--- a/tests/lean/run/async_dns.lean
+++ b/tests/lean/run/async_dns.lean
@@ -31,6 +31,32 @@ def runDNSNoAscii : Async Unit := do
   unless infos.size > 0 do
     (throw <| IO.userError <| "No DNS results for google.com" : IO _)
 
+  let ipv4 := infos.filterMap (fun | .v4 e => some e | _ => none)
+
+  if let some head := ipv4[0]? then
+    let parts : Vector UInt8 4 := head.octets
+
+    let isValid :=
+      -- Not in 0.0.0.0/8 (current network)
+      parts[0] != 0 &&
+      -- Not in 10.0.0.0/8 (private)
+      parts[0] != 10 &&
+      -- Not in 127.0.0.0/8 (loopback)
+      parts[0] != 127 &&
+      -- Not in 169.254.0.0/16 (link-local)
+      !(parts[0] == 169 && parts[1] == 254) &&
+      -- Not in 172.16.0.0/12 (private)
+      !(parts[0] == 172 && parts[1] >= 16 && parts[1] <= 31) &&
+      -- Not in 192.168.0.0/16 (private)
+      !(parts[0] == 192 && parts[1] == 168) &&
+      -- Not in 224.0.0.0/4 (multicast)
+      parts[0] < 224 &&
+      -- Not 255.255.255.255 (broadcast)
+      !(parts[0] == 255 && parts[1] == 255 && parts[2] == 255 && parts[3] == 255)
+
+    unless isValid do
+      throw <| IO.userError <| s!"Invalid IP address for google.com: {parts[0]}.{parts[1]}.{parts[2]}.{parts[3]}"
+
 def runReverseDNS : Async Unit := do
   let result ← DNS.getNameInfo (.v4 ⟨.ofParts 8 8 8 8, 53⟩)
   assertBEq result.service "domain"