From 6cbd810206a3a5c7bd5f959267cdb8fbfffa2f1e Mon Sep 17 00:00:00 2001
From: "Sergio R. Caprile" <scaprile@cesanta.com>
Date: Tue, 28 Jul 2026 14:36:40 -0300
Subject: [PATCH] improve mg_aton6 and tests

---
 mongoose.c       | 31 +++++++++++++++++++++----------
 src/net.c        | 31 +++++++++++++++++++++----------
 test/unit_test.c |  7 +++++++
 3 files changed, 49 insertions(+), 20 deletions(-)

diff --git a/mongoose.c b/mongoose.c
index 01627d18..603758a7 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -7883,22 +7883,31 @@ static bool mg_v4mapped(struct mg_str str, struct mg_addr *addr) {
 
 static bool mg_aton6(struct mg_str str, struct mg_addr *addr) {
   size_t i, j = 0, n = 0, dc = 42;
+  uint16_t val = 0;
+  bool have = false;
   addr->scope_id = 0;
   if (str.len > 2 && str.buf[0] == '[') str.buf++, str.len -= 2;
   if (mg_v4mapped(str, addr)) return true;  // sets addr->is_ip6
   for (i = 0; i < str.len; i++) {
-    if ((str.buf[i] >= '0' && str.buf[i] <= '9') ||
-        (str.buf[i] >= 'a' && str.buf[i] <= 'f') ||
-        (str.buf[i] >= 'A' && str.buf[i] <= 'F')) {
-      unsigned long val = 0;  // TODO(): This loops on chars, refactor
+    int x = str.buf[i] >= '0' && str.buf[i] <= '9'   ? str.buf[i] - '0'
+            : str.buf[i] >= 'a' && str.buf[i] <= 'f' ? str.buf[i] - 'a' + 10
+            : str.buf[i] >= 'A' && str.buf[i] <= 'F' ? str.buf[i] - 'A' + 10
+                                                     : -1;
+    if (x >= 0) {
       if (i > j + 3) return false;
-      // MG_DEBUG(("%lu %lu [%.*s]", i, j, (int) (i - j + 1), &str.buf[j]));
-      mg_str_to_num(mg_str_n(&str.buf[j], i - j + 1), 16, &val, sizeof(val));
-      addr->addr.ip[n] = (uint8_t) ((val >> 8) & 255);
-      addr->addr.ip[n + 1] = (uint8_t) (val & 255);
-    } else if (str.buf[i] == ':') {
+      val = (uint16_t) ((val << 4) | (uint16_t) x);
+      have = true;
+      continue;
+    }
+    if (have) {
+      addr->addr.ip[n] = (uint8_t) (val >> 8),
+      addr->addr.ip[n + 1] = (uint8_t) val;
+      val = 0, have = false;
+    }
+    if (str.buf[i] == ':') {
       j = i + 1;
       if (i > 0 && str.buf[i - 1] == ':') {
+        if (dc != 42) return false;
         dc = n;  // Double colon
         if (i > 1 && str.buf[i - 2] == ':') return false;
       } else if (i > 0) {
@@ -7918,12 +7927,14 @@ static bool mg_aton6(struct mg_str str, struct mg_addr *addr) {
       return false;
     }
   }
+  if (have)
+    addr->addr.ip[n] = (uint8_t) (val >> 8),
+    addr->addr.ip[n + 1] = (uint8_t) val;
   if (n < 14 && dc == 42) return false;
   if (n < 14) {
     memmove(&addr->addr.ip[dc + (14 - n)], &addr->addr.ip[dc], n - dc + 2);
     memset(&addr->addr.ip[dc], 0, 14 - n);
   }
-
   addr->is_ip6 = true;
   return true;
 }
diff --git a/src/net.c b/src/net.c
index c2dd53b5..4211d4b3 100644
--- a/src/net.c
+++ b/src/net.c
@@ -85,22 +85,31 @@ static bool mg_v4mapped(struct mg_str str, struct mg_addr *addr) {
 
 static bool mg_aton6(struct mg_str str, struct mg_addr *addr) {
   size_t i, j = 0, n = 0, dc = 42;
+  uint16_t val = 0;
+  bool have = false;
   addr->scope_id = 0;
   if (str.len > 2 && str.buf[0] == '[') str.buf++, str.len -= 2;
   if (mg_v4mapped(str, addr)) return true;  // sets addr->is_ip6
   for (i = 0; i < str.len; i++) {
-    if ((str.buf[i] >= '0' && str.buf[i] <= '9') ||
-        (str.buf[i] >= 'a' && str.buf[i] <= 'f') ||
-        (str.buf[i] >= 'A' && str.buf[i] <= 'F')) {
-      unsigned long val = 0;  // TODO(): This loops on chars, refactor
+    int x = str.buf[i] >= '0' && str.buf[i] <= '9'   ? str.buf[i] - '0'
+            : str.buf[i] >= 'a' && str.buf[i] <= 'f' ? str.buf[i] - 'a' + 10
+            : str.buf[i] >= 'A' && str.buf[i] <= 'F' ? str.buf[i] - 'A' + 10
+                                                     : -1;
+    if (x >= 0) {
       if (i > j + 3) return false;
-      // MG_DEBUG(("%lu %lu [%.*s]", i, j, (int) (i - j + 1), &str.buf[j]));
-      mg_str_to_num(mg_str_n(&str.buf[j], i - j + 1), 16, &val, sizeof(val));
-      addr->addr.ip[n] = (uint8_t) ((val >> 8) & 255);
-      addr->addr.ip[n + 1] = (uint8_t) (val & 255);
-    } else if (str.buf[i] == ':') {
+      val = (uint16_t) ((val << 4) | (uint16_t) x);
+      have = true;
+      continue;
+    }
+    if (have) {
+      addr->addr.ip[n] = (uint8_t) (val >> 8),
+      addr->addr.ip[n + 1] = (uint8_t) val;
+      val = 0, have = false;
+    }
+    if (str.buf[i] == ':') {
       j = i + 1;
       if (i > 0 && str.buf[i - 1] == ':') {
+        if (dc != 42) return false;
         dc = n;  // Double colon
         if (i > 1 && str.buf[i - 2] == ':') return false;
       } else if (i > 0) {
@@ -120,12 +129,14 @@ static bool mg_aton6(struct mg_str str, struct mg_addr *addr) {
       return false;
     }
   }
+  if (have)
+    addr->addr.ip[n] = (uint8_t) (val >> 8),
+    addr->addr.ip[n + 1] = (uint8_t) val;
   if (n < 14 && dc == 42) return false;
   if (n < 14) {
     memmove(&addr->addr.ip[dc + (14 - n)], &addr->addr.ip[dc], n - dc + 2);
     memset(&addr->addr.ip[dc], 0, 14 - n);
   }
-
   addr->is_ip6 = true;
   return true;
 }
diff --git a/test/unit_test.c b/test/unit_test.c
index e8af21f7..f35ccae9 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -2855,6 +2855,13 @@ static void test_util(void) {
   e = "\x20\x01\x48\x60\x48\x60\x00\x00\x00\x00\x00\x00\x00\x00\x88\x88";
   ASSERT(memcmp(&a.addr.ip6, e, sizeof(a.addr.ip6)) == 0);
 
+  ASSERT(mg_aton(mg_str("12345::1"), &a) == false);
+  ASSERT(mg_aton(mg_str("1:::2"), &a) == false);
+  ASSERT(mg_aton(mg_str("1::2::3"), &a) == false);
+  ASSERT(mg_aton(mg_str("1:2:3:4:5:6:7"), &a) == false);
+  ASSERT(mg_aton(mg_str("1:2:3:4:5:6:7:8:9"), &a) == false);
+  ASSERT(mg_aton(mg_str("1:2:3:4:5:6:7:g"), &a) == false);
+
   ASSERT(mg_url_decode("a=%", 3, buf, sizeof(buf), 0) < 0);
   ASSERT(mg_url_decode("&&&a=%", 6, buf, sizeof(buf), 0) < 0);
   ASSERT(mg_url_decode("a=%1", 4, buf, sizeof(buf), 0) < 0);