Use ASNs for mapped IPv4 addresses correctly

sipa · furszy · commit e527e04aeed2 · 2021-07-28T10:40:53.000-03:00
diff --git a/src/netaddress.cpp b/src/netaddress.cpp
@@ -317,6 +317,26 @@ bool CNetAddr::GetIn6Addr(struct in6_addr* pipv6Addr) const
     return true;
 }
 
+bool CNetAddr::HasLinkedIPv4() const
+{
+    return IsRoutable() && (IsIPv4() || IsRFC6145() || IsRFC6052() || IsRFC3964() || IsRFC4380());
+}
+
+uint32_t CNetAddr::GetLinkedIPv4() const
+{
+    if (IsIPv4() || IsRFC6145() || IsRFC6052()) {
+        // IPv4, mapped IPv4, SIIT translated IPv4: the IPv4 address is the last 4 bytes of the address
+        return ReadBE32(ip + 12);
+    } else if (IsRFC3964()) {
+        // 6to4 tunneled IPv4: the IPv4 address is in bytes 2-6
+        return ReadBE32(ip + 2);
+    } else if (IsRFC4380()) {
+        // Teredo tunneled IPv4: the IPv4 address is in the last 4 bytes of the address, but bitflipped
+        return ~ReadBE32(ip + 12);
+    }
+    assert(false);
+}
+
 uint32_t CNetAddr::GetNetClass() const {
     uint32_t net_class = NET_IPV6;
     if (IsLocal()) {
@@ -326,7 +346,7 @@ uint32_t CNetAddr::GetNetClass() const {
         net_class = NET_INTERNAL;
     } else if (!IsRoutable()) {
         net_class = NET_UNROUTABLE;
-    } else if (IsIPv4() || IsRFC6145() || IsRFC6052() || IsRFC3964() || IsRFC4380()) {
+    } else if (HasLinkedIPv4()) {
         net_class = NET_IPV4;
     } else if (IsTor()) {
         net_class = NET_ONION;
@@ -340,10 +360,24 @@ uint32_t CNetAddr::GetMappedAS(const std::vector<bool> &asmap) const {
         return 0; // Indicates not found, safe because AS0 is reserved per RFC7607.
     }
     std::vector<bool> ip_bits(128);
-    for (int8_t byte_i = 0; byte_i < 16; ++byte_i) {
-        uint8_t cur_byte = GetByte(15 - byte_i);
-        for (uint8_t bit_i = 0; bit_i < 8; ++bit_i) {
-            ip_bits[byte_i * 8 + bit_i] = (cur_byte >> (7 - bit_i)) & 1;
+    if (HasLinkedIPv4()) {
+        // For lookup, treat as if it was just an IPv4 address (pchIPv4 prefix + IPv4 bits)
+        for (int8_t byte_i = 0; byte_i < 12; ++byte_i) {
+            for (uint8_t bit_i = 0; bit_i < 8; ++bit_i) {
+                ip_bits[byte_i * 8 + bit_i] = (pchIPv4[byte_i] >> (7 - bit_i)) & 1;
+            }
+        }
+        uint32_t ipv4 = GetLinkedIPv4();
+        for (int i = 0; i < 32; ++i) {
+            ip_bits[96 + i] = (ipv4 >> (31 - i)) & 1;
+        }
+    } else {
+        // Use all 128 bits of the IPv6 address otherwise
+        for (int8_t byte_i = 0; byte_i < 16; ++byte_i) {
+            uint8_t cur_byte = GetByte(15 - byte_i);
+            for (uint8_t bit_i = 0; bit_i < 8; ++bit_i) {
+                ip_bits[byte_i * 8 + bit_i] = (cur_byte >> (7 - bit_i)) & 1;
+            }
         }
     }
     uint32_t mapped_as = Interpret(asmap, ip_bits);
@@ -379,51 +413,32 @@ std::vector<unsigned char> CNetAddr::GetGroup(const std::vector<bool> &asmap) co
     int nStartByte = 0;
     int nBits = 16;
 
-    // all local addresses belong to the same group
-    if (IsLocal())
-    {
+    if (IsLocal()) {
+        // all local addresses belong to the same group
         nBits = 0;
-    }
-    // all internal-usage addresses get their own group
-    if (IsInternal())
-    {
+    } else if (IsInternal()) {
+        // all internal-usage addresses get their own group
         nStartByte = sizeof(g_internal_prefix);
         nBits = (sizeof(ip) - sizeof(g_internal_prefix)) * 8;
-    }
-    // all other unroutable addresses belong to the same group
-    else if (!IsRoutable())
-    {
+    } else if (!IsRoutable()) {
+        // all other unroutable addresses belong to the same group
         nBits = 0;
-    }
-    // for IPv4 addresses, '1' + the 16 higher-order bits of the IP
-    // includes mapped IPv4, SIIT translated IPv4, and the well-known prefix
-    else if (IsIPv4() || IsRFC6145() || IsRFC6052())
-    {
-        nStartByte = 12;
-    }
-    // for 6to4 tunnelled addresses, use the encapsulated IPv4 address
-    else if (IsRFC3964())
-    {
-        nStartByte = 2;
-    }
-    // for Teredo-tunnelled IPv6 addresses, use the encapsulated IPv4 address
-    else if (IsRFC4380())
-    {
-        vchRet.push_back(GetByte(3) ^ 0xFF);
-        vchRet.push_back(GetByte(2) ^ 0xFF);
+    } else if (HasLinkedIPv4()) {
+        // IPv4 addresses (and mapped IPv4 addresses) use /16 groups
+        uint32_t ipv4 = GetLinkedIPv4();
+        vchRet.push_back((ipv4 >> 24) & 0xFF);
+        vchRet.push_back((ipv4 >> 16) & 0xFF);
         return vchRet;
-    }
-    else if (IsTor())
-    {
+    } else if (IsTor()) {
         nStartByte = 6;
         nBits = 4;
-    }
-    // for he.net, use /36 groups
-    else if (GetByte(15) == 0x20 && GetByte(14) == 0x01 && GetByte(13) == 0x04 && GetByte(12) == 0x70)
+    } else if (GetByte(15) == 0x20 && GetByte(14) == 0x01 && GetByte(13) == 0x04 && GetByte(12) == 0x70) {
+        // for he.net, use /36 groups
         nBits = 36;
-    // for the rest of the IPv6 network, use /32 groups
-    else
+    } else {
+        // for the rest of the IPv6 network, use /32 groups
         nBits = 32;
+    }
 
     // push our ip onto vchRet byte by byte...
     while (nBits >= 8)
diff --git a/src/netaddress.h b/src/netaddress.h
@@ -82,6 +82,11 @@ class CNetAddr
     bool GetInAddr(struct in_addr* pipv4Addr) const;
     uint32_t GetNetClass() const;
 
+    //! For IPv4, mapped IPv4, SIIT translated IPv4, Teredo, 6to4 tunneled addresses, return the relevant IPv4 address as a uint32.
+    uint32_t GetLinkedIPv4() const;
+    //! Whether this address has a linked IPv4 address (see GetLinkedIPv4()).
+    bool HasLinkedIPv4() const;
+
     // The AS on the BGP path to the node we use to diversify
     // peers in AddrMan bucketing based on the AS infrastructure.
     // The ip->AS mapping depends on how asmap is constructed.
