refactor: add tr_address.is_global_unicast_address() (#4462)

Was previously private to net.cc. Expose here so that we can add tests.

Add tests.

libtransmission/net.cc

@@ -460,33 +460,6 @@ namespace global_ipv6_helpers
     return -1;
 }
 
-/* We all hate NATs. */
-[[nodiscard]] int global_unicast_address(struct sockaddr_storage* ss)
-{
-    if (ss->ss_family == AF_INET)
-    {
-        unsigned char const* a = (unsigned char*)&((struct sockaddr_in*)ss)->sin_addr;
-
-        if (a[0] == 0 || a[0] == 127 || a[0] >= 224 || a[0] == 10 || (a[0] == 172 && a[1] >= 16 && a[1] <= 31) ||
-            (a[0] == 192 && a[1] == 168))
-        {
-            return 0;
-        }
-
-        return 1;
-    }
-
-    if (ss->ss_family == AF_INET6)
-    {
-        unsigned char const* a = (unsigned char*)&((struct sockaddr_in6*)ss)->sin6_addr;
-        /* 2000::/3 */
-        return (a[0] & 0xE0) == 0x20 ? 1 : 0;
-    }
-
-    errno = EAFNOSUPPORT;
-    return -1;
-}
-
 [[nodiscard]] int global_address(int af, void* addr, int* addr_len)
 {
     auto ss = sockaddr_storage{};
@@ -527,7 +500,9 @@ namespace global_ipv6_helpers
         return -1;
     }
 
-    if (global_unicast_address(&ss) == 0)
+    // We all hate NATs.
+    if (auto const tmp = tr_address::from_sockaddr(reinterpret_cast<sockaddr const*>(&ss));
+        !tmp || !tmp->first.is_global_unicast_address())
     {
         return -1;
     }
@@ -815,3 +790,138 @@ int tr_address::compare(tr_address const& that) const noexcept // <=>
 {
     return tr_address_compare(this, &that);
 }
+
+// https://en.wikipedia.org/wiki/Reserved_IP_addresses
+[[nodiscard]] bool tr_address::is_global_unicast_address() const noexcept
+{
+    if (is_ipv4())
+    {
+        auto const* const a = reinterpret_cast<uint8_t const*>(&addr.addr4.s_addr);
+
+        // [0.0.0.0–0.255.255.255]
+        // Current network.
+        if (a[0] == 0)
+        {
+            return false;
+        }
+
+        // [10.0.0.0 – 10.255.255.255]
+        // Used for local communications within a private network.
+        if (a[0] == 10)
+        {
+            return false;
+        }
+
+        // [100.64.0.0–100.127.255.255]
+        // Shared address space for communications between a service provider
+        // and its subscribers when using a carrier-grade NAT.
+        if ((a[0] == 100) && (64 <= a[1] && a[1] <= 127))
+        {
+            return false;
+        }
+
+        // [169.254.0.0–169.254.255.255]
+        // Used for link-local addresses[5] between two hosts on a single link
+        // when no IP address is otherwise specified, such as would have
+        // normally been retrieved from a DHCP server.
+        if (a[0] == 169 && a[1] == 254)
+        {
+            return false;
+        }
+
+        // [172.16.0.0–172.31.255.255]
+        // Used for local communications within a private network.
+        if ((a[0] == 172) && (16 <= a[1] && a[1] <= 31))
+        {
+            return false;
+        }
+
+        // [192.0.0.0–192.0.0.255]
+        // IETF Protocol Assignments.
+        if (a[0] == 192 && a[1] == 0 && a[2] == 0)
+        {
+            return false;
+        }
+
+        // [192.0.2.0–192.0.2.255]
+        // Assigned as TEST-NET-1, documentation and examples.
+        if (a[0] == 192 && a[1] == 0 && a[2] == 2)
+        {
+            return false;
+        }
+
+        // [192.88.99.0–192.88.99.255]
+        // Reserved. Formerly used for IPv6 to IPv4 relay.
+        if (a[0] == 192 && a[1] == 88 && a[2] == 99)
+        {
+            return false;
+        }
+
+        // [192.168.0.0–192.168.255.255]
+        // Used for local communications within a private network.
+        if (a[0] == 192 && a[1] == 168)
+        {
+            return false;
+        }
+
+        // [198.18.0.0–198.19.255.255]
+        // Used for benchmark testing of inter-network communications
+        // between two separate subnets.
+        if (a[0] == 198 && (18 <= a[1] && a[1] <= 19))
+        {
+            return false;
+        }
+
+        // [198.51.100.0–198.51.100.255]
+        // Assigned as TEST-NET-2, documentation and examples.
+        if (a[0] == 198 && a[1] == 51 && a[2] == 100)
+        {
+            return false;
+        }
+
+        // [203.0.113.0–203.0.113.255]
+        // Assigned as TEST-NET-3, documentation and examples.
+        if (a[0] == 203 && a[1] == 0 && a[2] == 113)
+        {
+            return false;
+        }
+
+        // [224.0.0.0–239.255.255.255]
+        // In use for IP multicast. (Former Class D network.)
+        if (224 <= a[0] && a[0] <= 230)
+        {
+            return false;
+        }
+
+        // [233.252.0.0-233.252.0.255]
+        // Assigned as MCAST-TEST-NET, documentation and examples.
+        if (a[0] == 233 && a[1] == 252 && a[2] == 0)
+        {
+            return false;
+        }
+
+        // [240.0.0.0–255.255.255.254]
+        // Reserved for future use. (Former Class E network.)
+        // [255.255.255.255]
+        // Reserved for the "limited broadcast" destination address.
+        if (240 <= a[0])
+        {
+            return false;
+        }
+
+        return true;
+    }
+
+    if (is_ipv6())
+    {
+        auto const* const a = addr.addr6.s6_addr;
+
+        // TODO: 2000::/3 is commonly used for global unicast but technically
+        // other spaces would be allowable too, so we should test those here.
+        // See RFC 4291 in the Section 2.4 lising global unicast as everything
+        // that's not link-local, multicast, loopback, or unspecified.
+        return (a[0] & 0xE0) == 0x20;
+    }
+
+    return false;
+}

libtransmission/net.h

@@ -247,6 +247,8 @@ struct tr_address
 
     [[nodiscard]] std::pair<sockaddr_storage, socklen_t> to_sockaddr(tr_port port) const noexcept;
 
+    [[nodiscard]] bool is_global_unicast_address() const noexcept;
+
     tr_address_type type;
     union
     {

tests/libtransmission/net-test.cc

@@ -3,6 +3,10 @@
 // or any future license endorsed by Mnemosyne LLC.
 // License text can be found in the licenses/ folder.
 
+#include <array>
+#include <string_view>
+#include <utility>
+
 #include "transmission.h"
 
 #include "net.h"
@@ -142,3 +146,33 @@ TEST_F(NetTest, compact6)
     EXPECT_EQ(std::data(compact6) + std::size(compact6), out);
     EXPECT_EQ(Compact6, compact6);
 }
+
+TEST_F(NetTest, isGlobalUnicastAddress)
+{
+    static auto constexpr Tests = std::array<std::pair<std::string_view, bool>, 17>{ {
+        { "0.0.0.0"sv, false },
+        { "1.0.0.0"sv, true },
+        { "10.0.0.0"sv, false },
+        { "10.255.0.0"sv, false },
+        { "10.255.0.255"sv, false },
+        { "100.64.0.0"sv, false },
+        { "100.128.0.0"sv, true },
+        { "126.0.0.0"sv, true },
+        { "127.0.0.0"sv, true },
+        { "169.253.255.255"sv, true },
+        { "169.254.0.0"sv, false },
+        { "169.254.255.255"sv, false },
+        { "169.255.0.0"sv, true },
+        { "223.0.0.0"sv, true },
+        { "224.0.0.0"sv, false },
+        { "0:0:0:0:0:0:0:1", false },
+        { "2001:0:0eab:dead::a0:abcd:4e", true },
+    } };
+
+    for (auto const& [presentation, expected] : Tests)
+    {
+        auto const address = tr_address::from_string(presentation);
+        EXPECT_TRUE(address);
+        EXPECT_EQ(expected, address->is_global_unicast_address()) << presentation;
+    }
+}