Merge #20852: net: allow CSubNet of non-IP networks

39b43298d9c54f9c18bef36f3d5934f57aefd088 test: add test for banning of non-IP addresses (Vasil Dimov)
94d335da7f8232bc653c9b08b0a33b517b4c98ad net: allow CSubNet of non-IP networks (Vasil Dimov)

Pull request description:

  Allow creation of valid `CSubNet` objects of non-IP networks and only
  match the single address they were created from (like /32 for IPv4 or
  /128 for IPv6).

  This fixes a deficiency in `CConnman::DisconnectNode(const CNetAddr& addr)`
  and in `BanMan` which assume that creating a subnet from any address
  using the `CSubNet(CNetAddr)` constructor would later match that address
  only. Before this change a non-IP subnet would be invalid and would not
  match any address.

ACKs for top commit:
  jonatack:
    Code review re-ACK 39b43298d9c54f9c18bef36f3d5934f57aefd088 per `git diff 5e95ce6 39b4329`; only change since last review is improvements to the functional test; verified the test fails on master @ 616eace0 where expected (`assert(self.is_banned(node, tor_addr))` fails and unban unfails)
  laanwj:
    code review ACK 39b43298d9c54f9c18bef36f3d5934f57aefd088

Tree-SHA512: 3239b26d0f2fa2d1388b4fdbc1d05ce4ac1980be699c6ec46049409baefcb2006b1e72b889871e2210e897f6725c48e873f68457eea7e6e4958ab4f959d20297

1 files changed, 23 insertions, 1 deletions

diff --git a/src/netaddress.h b/src/netaddress.h
index cf878fe374..b9eade7fd5 100644
--- a/src/netaddress.h
+++ b/src/netaddress.h
@@ -462,11 +462,33 @@ class CSubNet
         bool SanityCheck() const;
 
     public:
+        /**
+         * Construct an invalid subnet (empty, `Match()` always returns false).
+         */
         CSubNet();
+
+        /**
+         * Construct from a given network start and number of bits (CIDR mask).
+         * @param[in] addr Network start. Must be IPv4 or IPv6, otherwise an invalid subnet is
+         * created.
+         * @param[in] mask CIDR mask, must be in [0, 32] for IPv4 addresses and in [0, 128] for
+         * IPv6 addresses. Otherwise an invalid subnet is created.
+         */
         CSubNet(const CNetAddr& addr, uint8_t mask);
+
+        /**
+         * Construct from a given network start and mask.
+         * @param[in] addr Network start. Must be IPv4 or IPv6, otherwise an invalid subnet is
+         * created.
+         * @param[in] mask Network mask, must be of the same type as `addr` and not contain 0-bits
+         * followed by 1-bits. Otherwise an invalid subnet is created.
+         */
         CSubNet(const CNetAddr& addr, const CNetAddr& mask);
 
-        //constructor for single ip subnet (<ipv4>/32 or <ipv6>/128)
+        /**
+         * Construct a single-host subnet.
+         * @param[in] addr The sole address to be contained in the subnet, can also be non-IPv[46].
+         */
         explicit CSubNet(const CNetAddr& addr);
 
         bool Match(const CNetAddr &addr) const;