Net: Implement SO_LINGER

SO_LINGER allows specifying a timeout interval during which the socket attempts to send any remaining data before closing. If all data is ACKed within the specified timeout, the connection is closed gracefully using a FIN/ACK exchange. If the timeout expires with unacknowledged data, the socket is forcefully closed using RST, discarding any unsent data.
SerenityOS · Sep 27, 2024 · 175d986 · 175d986
1 parent c03be8e
commit 175d986
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Showing 3 changed files with 38 additions and 1 deletion.
diff --git a/Kernel/Net/Socket.cpp b/Kernel/Net/Socket.cpp
@@ -136,6 +136,12 @@ ErrorOr<void> Socket::setsockopt(int level, int option, Userspace<void const*> u
         m_broadcast_allowed = TRY(copy_typed_from_user(static_ptr_cast<int const*>(user_value))) != 0;
         return {};
     }
+    case SO_LINGER: {
+        if (user_value_size != sizeof(linger))
+            return EINVAL;
+        m_linger = TRY(copy_typed_from_user(static_ptr_cast<linger const*>(user_value)));
+        return {};
+    }
     default:
         dbgln("setsockopt({}) at SOL_SOCKET not implemented.", option);
         return ENOPROTOOPT;
@@ -257,6 +263,13 @@ ErrorOr<void> Socket::getsockopt(OpenFileDescription&, int level, int option, Us
         size = sizeof(broadcast_allowed);
         return copy_to_user(value_size, &size);
     }
+    case SO_LINGER: {
+        if (size < sizeof(linger))
+            return EINVAL;
+        TRY(copy_to_user(static_ptr_cast<linger*>(value), &m_linger));
+        size = sizeof(linger);
+        return copy_to_user(value_size, &size);
+    }
     default:
         dbgln("getsockopt({}) at SOL_SOCKET not implemented.", option);
         return ENOPROTOOPT;

diff --git a/Kernel/Net/Socket.h b/Kernel/Net/Socket.h
@@ -157,6 +157,7 @@ class Socket : public File {
     ucred m_acceptor { 0, 0, 0 };
     bool m_routing_disabled { false };
     bool m_broadcast_allowed { false };
+    linger m_linger { 0, 0 };
 
 private:
     virtual bool is_socket() const final { return true; }

diff --git a/Kernel/Net/TCPSocket.cpp b/Kernel/Net/TCPSocket.cpp
@@ -664,8 +664,31 @@ ErrorOr<void> TCPSocket::close()
 {
     MutexLocker locker(mutex());
     auto result = IPv4Socket::close();
+    if (m_linger.l_onoff != 0) {
+        if (m_linger.l_linger > 0) {
+            dbgln_if(TCP_SOCKET_DEBUG, "TCPSocket({}) SO_LINGER with {} seconds interval", this, m_linger.l_linger);
+            auto deadline = TimeManagement::the().current_time(CLOCK_MONOTONIC_COARSE) + Duration::from_seconds(m_linger.l_linger);
+            // FIXME: Make this return earlier if all data is acknowledged before end of interval
+            (void)TimerQueue::the().add_timer_without_id(*m_timer, CLOCK_MONOTONIC_COARSE, deadline, [&]() {
+                bool has_unacked_data = m_unacked_packets.with_shared([&](auto const& packets) { return packets.size > 0; });
+                if (has_unacked_data) {
+                    dbgln_if(TCP_SOCKET_DEBUG, "TCPSocket({}) SO_LINGER interval expired. Some data couldn't make it :(", this);
+                    drop_receive_buffer();
+                    (void)send_tcp_packet(TCPFlags::RST);
+                    do_state_closed();
+                    return;
+                }
+                dbgln_if(TCP_SOCKET_DEBUG, "TCPSocket({}) SO_LINGER timeout. All remaining data has been acknowledged, closing gracefully", this);
+            });
+        } else {
+            dbgln_if(TCP_SOCKET_DEBUG, "TCPSocket({}) SO_LINGER without timeout, closing immediately", this);
+            (void)send_tcp_packet(TCPFlags::RST);
+            do_state_closed();
+        }
+    }
+
     if (state() == State::CloseWait) {
-        dbgln_if(TCP_SOCKET_DEBUG, " Sending FIN from CloseWait and moving into LastAck");
+        dbgln_if(TCP_SOCKET_DEBUG, "TCPSocket({}) Sending FIN from CloseWait and moving into LastAck", this);
         [[maybe_unused]] auto rc = send_tcp_packet(TCPFlags::FIN | TCPFlags::ACK);
         set_state(State::LastAck);
     }