Merge #19845: net: CNetAddr: add support to (un)serialize as ADDRv2

7be6ff6187 net: recognize TORv3/I2P/CJDNS networks (Vasil Dimov)
e0d73573a3 net: CNetAddr: add support to (un)serialize as ADDRv2 (Vasil Dimov)
fe42411b4b test: move HasReason so it can be reused (Vasil Dimov)
d2bb681f96 util: move HasPrefix() so it can be reused (Vasil Dimov)

Pull request description:

  (chopped off from #19031 to ease review)

  Add an optional support to serialize/unserialize `CNetAddr` in ADDRv2 format (BIP155). The new serialization is engaged by ORing a flag into the stream version.

  So far this is only used in tests to ensure the new code works as expected.

ACKs for top commit:
  Sjors:
    re-tACK 7be6ff6187
  sipa:
    re-utACK 7be6ff6187
  eriknylund:
    ACK 7be6ff6187 I built the PR on macOS Catalina 10.15.6, ran both tests and functional tests. I've reviewed the code and think the changes look good and according to BIP155. I verified that the added Base32 encoding test looks as proposed and working. I've run a node for a week only with Onion addresses `-onlynet=onion` without issues and I can connect to other peer reviewers running TorV3 on their nodes and I can connect both of my test nodes to each other.
  jonatack:
    re-ACK 7be6ff6187 per `git diff b9c46e0 7be6ff6`, debug build, ran/running bitcoind with this change and observed the log and `-netinfo` peer connections while connected as a tor v2 service to both tor v2 peers and also five tor v3 peers.
  hebasto:
    ACK 7be6ff6187, tested on Linux Mint 20 (x86_64): on top of this pull and #19031 I'm able to connect to onion v3 addresses, and jonatack is able to connect to my created onion v3 address.

Tree-SHA512: dc621411ac4393993aa3ccad10991717ec5f9f2643cae46a24a89802df0a33d6042994fc8ff2f0f397a3dbcd1c0e58fe4724305a2f9eb64d9342c3bdf784d9be

src/util/strencodings.cpp

@@ -201,20 +201,24 @@ std::string DecodeBase64(const std::string& str, bool* pf_invalid)
     return std::string((const char*)vchRet.data(), vchRet.size());
 }
 
-std::string EncodeBase32(Span<const unsigned char> input)
+std::string EncodeBase32(Span<const unsigned char> input, bool pad)
 {
     static const char *pbase32 = "abcdefghijklmnopqrstuvwxyz234567";
 
     std::string str;
     str.reserve(((input.size() + 4) / 5) * 8);
     ConvertBits<8, 5, true>([&](int v) { str += pbase32[v]; }, input.begin(), input.end());
-    while (str.size() % 8) str += '=';
+    if (pad) {
+        while (str.size() % 8) {
+            str += '=';
+        }
+    }
     return str;
 }
 
-std::string EncodeBase32(const std::string& str)
+std::string EncodeBase32(const std::string& str, bool pad)
 {
-    return EncodeBase32(MakeUCharSpan(str));
+    return EncodeBase32(MakeUCharSpan(str), pad);
 }
 
 std::vector<unsigned char> DecodeBase32(const char* p, bool* pf_invalid)

src/util/strencodings.h

@@ -52,8 +52,20 @@ std::string EncodeBase64(Span<const unsigned char> input);
 std::string EncodeBase64(const std::string& str);
 std::vector<unsigned char> DecodeBase32(const char* p, bool* pf_invalid = nullptr);
 std::string DecodeBase32(const std::string& str, bool* pf_invalid = nullptr);
-std::string EncodeBase32(Span<const unsigned char> input);
-std::string EncodeBase32(const std::string& str);
+
+/**
+ * Base32 encode.
+ * If `pad` is true, then the output will be padded with '=' so that its length
+ * is a multiple of 8.
+ */
+std::string EncodeBase32(Span<const unsigned char> input, bool pad = true);
+
+/**
+ * Base32 encode.
+ * If `pad` is true, then the output will be padded with '=' so that its length
+ * is a multiple of 8.
+ */
+std::string EncodeBase32(const std::string& str, bool pad = true);
 
 void SplitHostPort(std::string in, int& portOut, std::string& hostOut);
 int64_t atoi64(const std::string& str);

src/util/string.h

@@ -7,6 +7,8 @@
 
 #include <attributes.h>
 
+#include <algorithm>
+#include <array>
 #include <cstring>
 #include <locale>
 #include <sstream>
@@ -74,4 +76,15 @@ std::string ToString(const T& t)
     return oss.str();
 }
 
+/**
+ * Check whether a container begins with the given prefix.
+ */
+template <typename T1, size_t PREFIX_LEN>
+NODISCARD inline bool HasPrefix(const T1& obj,
+                                const std::array<uint8_t, PREFIX_LEN>& prefix)
+{
+    return obj.size() >= PREFIX_LEN &&
+           std::equal(std::begin(prefix), std::end(prefix), std::begin(obj));
+}
+
 #endif // BITCOIN_UTIL_STRENCODINGS_H