[MAINT] Added setting CLOSING state when closing a socket

[ethouris]

1. setting SRTS_CLOSING state on a socket that was requested to be closed.
2. Added time tracking when closing a socket with tracked wiping to track the time taken for wiping out a socket.

[maxsharabayko]

Setting the state to SRTS_CLOSING reduces the time to actually free the listener socket from 4.5 s to 1.5 s.
Adding CSync::notify_one_relaxed(m_GCStopCond); at the end of CUDTUnited::close() further reduces the time to 1 second by notifying the GC thread to run a re-check.

[maxsharabayko]

Git Diff

(For my reference).

diff --git a/srtcore/api.cpp b/srtcore/api.cpp
index f052c96..955e535 100644
--- a/srtcore/api.cpp
+++ b/srtcore/api.cpp
@@ -1974,7 +1974,10 @@ int srt::CUDTUnited::close(CUDTSocket* s)
     if (s->m_Status == SRTS_LISTENING)
     {
         if (s->core().m_bBroken)
+        {
+            LOGC(smlog.Note, log << s->core().CONID() << "CLOSING (broken but listening)");
             return 0;
+        }

         s->m_tsClosureTimeStamp = steady_clock::now();
         s->core().m_bBroken     = true;
@@ -1988,8 +1991,9 @@ int srt::CUDTUnited::close(CUDTSocket* s)
         // be unable to bind to this port that the about-to-delete listener
         // is currently occupying (due to blocked slot in the RcvQueue).

-        HLOGC(smlog.Debug, log << s->core().CONID() << "CLOSING (removing listener immediately)");
+        LOGC(smlog.Note, log << s->core().CONID() << "CLOSING (removing listener immediately)");
         s->core().notListening();
+        s->m_Status = SRTS_CLOSING;

         // broadcast all "accept" waiting
         CSync::lock_notify_all(s->m_AcceptCond, s->m_AcceptLock);
@@ -2004,7 +2008,7 @@ int srt::CUDTUnited::close(CUDTSocket* s)
         s->core().closeInternal();

         // synchronize with garbage collection.
-        HLOGC(smlog.Debug,
+        LOGC(smlog.Note,
               log << "@" << u << "U::close done. GLOBAL CLOSE: " << s->core().CONID()
                   << "Acquiring GLOBAL control lock");
         ScopedLock manager_cg(m_GlobControlLock);
@@ -2119,6 +2123,8 @@ int srt::CUDTUnited::close(CUDTSocket* s)
     }
     */

+    CSync::notify_one_relaxed(m_GCStopCond);
+
     return 0;
 }

@@ -2602,6 +2608,7 @@ void srt::CUDTUnited::checkBrokenSockets()

         if (s->m_Status == SRTS_LISTENING)
         {
+            LOGC(smlog.Note, log << "checkBrokenSockets: @" << s->m_SocketID << " status LISTENING.");
             const steady_clock::duration elapsed = steady_clock::now() - s->m_tsClosureTimeStamp;
             // A listening socket should wait an extra 3 seconds
             // in case a client is connecting.
@@ -2616,6 +2623,7 @@ void srt::CUDTUnited::checkBrokenSockets()
         // available data is "ready to play").
                  && s->core().m_pRcvBuffer->hasAvailablePackets())
         {
+            LOGC(smlog.Note, log << "checkBrokenSockets: @" << s->m_SocketID << " m_pRcvBuffer has packets.");
             const int bc = s->core().m_iBrokenCounter.load();
             if (bc > 0)
             {
@@ -2634,7 +2642,7 @@ void srt::CUDTUnited::checkBrokenSockets()
         }
 #endif

-        HLOGC(smlog.Debug, log << "checkBrokenSockets: moving BROKEN socket to CLOSED: @" << i->first);
+        LOGC(smlog.Note, log << "checkBrokenSockets: moving BROKEN socket to CLOSED: @" << i->first);

         // close broken connections and start removal timer
         s->setClosed();

Unit Test

(No need to include it in the PR. Just for my reference).

#include <gtest/gtest.h>
#include <thread>
#include <chrono>
#include <string>
#include <map>

#ifdef _WIN32
#define INC_SRT_WIN_WINTIME // exclude gettimeofday from srt headers
#endif

#include "srt.h"

TEST(Listener, Restart)
{
    srt_startup();
    srt_setloglevel(LOG_NOTICE);

    auto s = srt_create_socket();

    sockaddr_in bind_sa;
    memset(&bind_sa, 0, sizeof bind_sa);
    bind_sa.sin_family = AF_INET;
    ASSERT_EQ(inet_pton(AF_INET, "127.0.0.1", &bind_sa.sin_addr), 1);
    bind_sa.sin_port = htons(5555);

    EXPECT_NE(srt_bind(s, (sockaddr*)&bind_sa, sizeof bind_sa), -1);
    EXPECT_NE(srt_listen(s, 5), -1);

    std::this_thread::sleep_for(std::chrono::milliseconds(500));

    srt_close(s);
    
    s = srt_create_socket();
    int optval = 100;
    int optlen = sizeof optval;
    EXPECT_NE(srt_setsockflag(s, SRTO_IPTTL, (void*)&optval, optlen), SRT_ERROR) << srt_getlasterror_str();

    const auto time_start = std::chrono::steady_clock::now();
    while (srt_bind(s, (sockaddr*)&bind_sa, sizeof bind_sa) == -1)
    {
        std::this_thread::sleep_for(std::chrono::milliseconds(500));
    }

    std::cerr << "Binding took " << std::chrono::duration_cast<std::chrono::milliseconds>((std::chrono::steady_clock::now() - time_start)).count() << '\n';

    //EXPECT_NE(srt_bind(s, (sockaddr*)&bind_sa, sizeof bind_sa), -1);
    EXPECT_NE(srt_listen(s, 5), -1);

    srt_close(s);
    srt_cleanup();
}