net: add new method Sock::SetSockOpt() that wraps setsockopt()

This will help to increase `Sock` usage and make more code mockable.

Author: vasild

src/test/fuzz/util.cpp

@@ -193,6 +193,19 @@ int FuzzedSock::GetSockOpt(int level, int opt_name, void* opt_val, socklen_t* op
     return 0;
 }
 
+int FuzzedSock::SetSockOpt(int, int, const void*, socklen_t) const
+{
+    constexpr std::array setsockopt_errnos{
+        ENOMEM,
+        ENOBUFS,
+    };
+    if (m_fuzzed_data_provider.ConsumeBool()) {
+        SetFuzzedErrNo(m_fuzzed_data_provider, setsockopt_errnos);
+        return -1;
+    }
+    return 0;
+}
+
 bool FuzzedSock::Wait(std::chrono::milliseconds timeout, Event requested, Event* occurred) const
 {
     constexpr std::array wait_errnos{

src/test/fuzz/util.h

@@ -68,6 +68,8 @@ class FuzzedSock : public Sock
 
     int GetSockOpt(int level, int opt_name, void* opt_val, socklen_t* opt_len) const override;
 
+    int SetSockOpt(int level, int opt_name, const void* opt_val, socklen_t opt_len) const override;
+
     bool Wait(std::chrono::milliseconds timeout, Event requested, Event* occurred = nullptr) const override;
 
     bool IsConnected(std::string& errmsg) const override;

src/test/util/net.h

@@ -150,6 +150,8 @@ class StaticContentsSock : public Sock
         return 0;
     }
 
+    int SetSockOpt(int, int, const void*, socklen_t) const override { return 0; }
+
     bool Wait(std::chrono::milliseconds timeout,
               Event requested,
               Event* occurred = nullptr) const override

src/util/sock.cpp

@@ -105,6 +105,11 @@ int Sock::GetSockOpt(int level, int opt_name, void* opt_val, socklen_t* opt_len)
     return getsockopt(m_socket, level, opt_name, static_cast<char*>(opt_val), opt_len);
 }
 
+int Sock::SetSockOpt(int level, int opt_name, const void* opt_val, socklen_t opt_len) const
+{
+    return setsockopt(m_socket, level, opt_name, static_cast<const char*>(opt_val), opt_len);
+}
+
 bool Sock::Wait(std::chrono::milliseconds timeout, Event requested, Event* occurred) const
 {
 #ifdef USE_POLL

src/util/sock.h

@@ -115,6 +115,16 @@ class Sock
                                          void* opt_val,
                                          socklen_t* opt_len) const;
 
+    /**
+     * setsockopt(2) wrapper. Equivalent to
+     * `setsockopt(this->Get(), level, opt_name, opt_val, opt_len)`. Code that uses this
+     * wrapper can be unit tested if this method is overridden by a mock Sock implementation.
+     */
+    [[nodiscard]] virtual int SetSockOpt(int level,
+                                         int opt_name,
+                                         const void* opt_val,
+                                         socklen_t opt_len) const;
+
     using Event = uint8_t;
 
     /**