Merge bitcoin/bitcoin#21879: refactor: wrap accept() and extend usage of Sock

6bf6e9fd9dece67878595a5f3361851c25833c49 net: change CreateNodeFromAcceptedSocket() to take Sock (Vasil Dimov)
9e3cbfca7c9efa620c0cce73503772805cc1fa82 net: use Sock in CConnman::ListenSocket (Vasil Dimov)
f8bd13f85ae5404adef23a52719d804a5c36b1e8 net: add new method Sock::Accept() that wraps accept() (Vasil Dimov)

Pull request description:

  _This is a piece of https://github.com/bitcoin/bitcoin/pull/21878, chopped off to ease review._

  Introduce an `accept(2)` wrapper `Sock::Accept()` and extend the usage of `Sock` in `CConnman::ListenSocket` and `CreateNodeFromAcceptedSocket()`.

ACKs for top commit:
  laanwj:
    Code review ACK 6bf6e9fd9dece67878595a5f3361851c25833c49
  jamesob:
    ACK 6bf6e9fd9dece67878595a5f3361851c25833c49 ([`jamesob/ackr/21879.2.vasild.wrap_accept_and_extend_u`](https://github.com/jamesob/bitcoin/tree/ackr/21879.2.vasild.wrap_accept_and_extend_u))
  jonatack:
    ACK 6bf6e9fd9dece67878595a5f3361851c25833c49 per `git range-diff ea989de 976f6e8 6bf6e9f` -- only change since my last review was `s/listen_socket.socket/listen_socket.sock->Get()/` in `src/net.cpp: CConnman::SocketHandlerListening()` -- re-read the code changes, rebase/debug build/ran units following my previous full review (https://github.com/bitcoin/bitcoin/pull/21879#pullrequestreview-761251278)
  w0xlt:
    tACK 6bf6e9f

Tree-SHA512: dc6d1acc4f255f1f7e8cf6dd74e97975cf3d5959e9fc2e689f74812ac3526d5ee8b6a32eca605925d10a4f7b6ff1ce5e900344311e587d19786b48c54d021b64

3 files changed, 36 insertions, 0 deletions

diff --git a/src/test/fuzz/util.cpp b/src/test/fuzz/util.cpp
index 5520eee758..f89b597eed 100644
--- a/src/test/fuzz/util.cpp
+++ b/src/test/fuzz/util.cpp
@@ -13,6 +13,8 @@
 #include <util/time.h>
 #include <version.h>
 
+#include <memory>
+
 FuzzedSock::FuzzedSock(FuzzedDataProvider& fuzzed_data_provider)
     : m_fuzzed_data_provider{fuzzed_data_provider}
 {
@@ -158,6 +160,20 @@ int FuzzedSock::Connect(const sockaddr*, socklen_t) const
     return 0;
 }
 
+std::unique_ptr<Sock> FuzzedSock::Accept(sockaddr* addr, socklen_t* addr_len) const
+{
+    constexpr std::array accept_errnos{
+        ECONNABORTED,
+        EINTR,
+        ENOMEM,
+    };
+    if (m_fuzzed_data_provider.ConsumeBool()) {
+        SetFuzzedErrNo(m_fuzzed_data_provider, accept_errnos);
+        return std::unique_ptr<FuzzedSock>();
+    }
+    return std::make_unique<FuzzedSock>(m_fuzzed_data_provider);
+}
+
 int FuzzedSock::GetSockOpt(int level, int opt_name, void* opt_val, socklen_t* opt_len) const
 {
     constexpr std::array getsockopt_errnos{
diff --git a/src/test/fuzz/util.h b/src/test/fuzz/util.h
index f4f8e9e70d..fd7f40c01d 100644
--- a/src/test/fuzz/util.h
+++ b/src/test/fuzz/util.h
@@ -401,6 +401,8 @@ public:
 
     int Connect(const sockaddr*, socklen_t) const override;
 
+    std::unique_ptr<Sock> Accept(sockaddr* addr, socklen_t* addr_len) const override;
+
     int GetSockOpt(int level, int opt_name, void* opt_val, socklen_t* opt_len) const override;
 
     bool Wait(std::chrono::milliseconds timeout, Event requested, Event* occurred = nullptr) const override;
diff --git a/src/test/util/net.h b/src/test/util/net.h
index 006e876c1a..20c45058a1 100644
--- a/src/test/util/net.h
+++ b/src/test/util/net.h
@@ -13,6 +13,7 @@
 #include <array>
 #include <cassert>
 #include <cstring>
+#include <memory>
 #include <string>
 
 struct ConnmanTestMsg : public CConnman {
@@ -126,6 +127,23 @@ public:
 
     int Connect(const sockaddr*, socklen_t) const override { return 0; }
 
+    std::unique_ptr<Sock> Accept(sockaddr* addr, socklen_t* addr_len) const override
+    {
+        if (addr != nullptr) {
+            // Pretend all connections come from 5.5.5.5:6789
+            memset(addr, 0x00, *addr_len);
+            const socklen_t write_len = static_cast<socklen_t>(sizeof(sockaddr_in));
+            if (*addr_len >= write_len) {
+                *addr_len = write_len;
+                sockaddr_in* addr_in = reinterpret_cast<sockaddr_in*>(addr);
+                addr_in->sin_family = AF_INET;
+                memset(&addr_in->sin_addr, 0x05, sizeof(addr_in->sin_addr));
+                addr_in->sin_port = htons(6789);
+            }
+        }
+        return std::make_unique<StaticContentsSock>("");
+    };
+
     int GetSockOpt(int level, int opt_name, void* opt_val, socklen_t* opt_len) const override
     {
         std::memset(opt_val, 0x0, *opt_len);