Merge bitcoin/bitcoin#26261: p2p: cleanup `LookupIntern`, `Lookup` and `LookupHost`

5c832c3820253affc65c0ed490e26e5b0a4d5c9b p2p, refactor: return `std::optional<CNetAddr>` in `LookupHost` (brunoerg)
34bcdfc6a65de906c65edccdd96fe15219081cd2 p2p, refactor: return vector/optional<CService> in `Lookup` (brunoerg)
7799eb125b7a1146f8251be5d26df574236212a9 p2p, refactor: return `std::vector<CNetAddr>` in `LookupHost` (brunoerg)
5c1774a563dcc237a88df69569cd94fe81e908f7 p2p, refactor: return `std::vector<CNetAddr>` in `LookupIntern` (brunoerg)

Pull request description:

  Continuation of #26078.

  To improve readability instead of returning a bool and passing stuff by reference, this PR changes:

  - `LookupHost` to return `std::vector<CNetAddr>`
  - `LookupHost` to return `std::optional<CNetAddr>`
  - `Lookup` to return `std::vector<CService>`
  - `Lookup` to return `std::optional<CService>`.
  - `LookupIntern` to return `std::vector<CNetAddr>`

  As discussed in #26078, it would be better to avoid using `optional` in some cases, but for specific `Lookup` and `LookupHost` functions it's necessary to use `optional` to verify if they were able to catch some data from their overloaded function.

ACKs for top commit:
  achow101:
    ACK 5c832c3820253affc65c0ed490e26e5b0a4d5c9b
  stickies-v:
    re-ACK 5c832c3820253affc65c0ed490e26e5b0a4d5c9b - just addressing two nits, no other changes
  theStack:
    re-ACK 5c832c3820253affc65c0ed490e26e5b0a4d5c9b

Tree-SHA512: ea346fdc54463999646269bd600cd4a1590ef958001d2f0fc2be608ca51e1b4365efccca76dd4972b023e12fcc6e67d226608b0df7beb901bdeadd19948df840

1 files changed, 7 insertions, 6 deletions

diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index f247e6ee91..a2a46ef32f 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -713,9 +713,10 @@ static RPCHelpMan setban()
         isSubnet = true;
 
     if (!isSubnet) {
-        CNetAddr resolved;
-        LookupHost(request.params[0].get_str(), resolved, false);
-        netAddr = resolved;
+        const std::optional<CNetAddr> addr{LookupHost(request.params[0].get_str(), false)};
+        if (addr.has_value()) {
+            netAddr = addr.value();
+        }
     }
     else
         LookupSubNet(request.params[0].get_str(), subNet);
@@ -943,11 +944,11 @@ static RPCHelpMan addpeeraddress()
     const bool tried{request.params[2].isNull() ? false : request.params[2].get_bool()};
 
     UniValue obj(UniValue::VOBJ);
-    CNetAddr net_addr;
+    std::optional<CNetAddr> net_addr{LookupHost(addr_string, false)};
     bool success{false};
 
-    if (LookupHost(addr_string, net_addr, false)) {
-        CService service{net_addr, port};
+    if (net_addr.has_value()) {
+        CService service{net_addr.value(), port};
         CAddress address{MaybeFlipIPv6toCJDNS(service), ServiceFlags{NODE_NETWORK | NODE_WITNESS}};
         address.nTime = Now<NodeSeconds>();
         // The source address is set equal to the address. This is equivalent to the peer