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Added immediate ACKs on Windows, similar to TCP_QUICKACK #101

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aljazdu wants to merge 2 commits into from
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Added immediate ACKs on Windows, similar to TCP_QUICKACK #101

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Added immediate ACKs on Windows, similar to TCP_QUICKACK
aljazdu Dec 10, 2025
a343947
Code cleanup
aljazdu Dec 11, 2025
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11 changes: 11 additions & 0 deletions src/pc/protocols/tcpip_host.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@
#pragma comment(lib, "iphlpapi.lib")
#define tcpip_errno WSAGetLastError()
#define ERRNO_EAGAIN WSAETIMEDOUT
#define SIO_TCP_SET_ACK_FREQUENCY _WSAIOW(IOC_VENDOR, 23)

#else

Expand Down Expand Up @@ -1116,6 +1117,16 @@ int tcpipPlatformConnect(const char *devPathRead, const char *devPathWrite, void
return -1;
}

#if (defined(_WIN32) || defined(_WIN64) )
// Force immediate ACKs
int freq = 1;
DWORD bytes;
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Copilot AI Dec 11, 2025

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The magic number 23 in _WSAIOW(IOC_VENDOR, 23) lacks explanation. Add a comment explaining that this is the Windows-specific code for TCP_MAXRT (or the specific ACK behavior being configured), as this vendor-specific ioctl code is not self-documenting.

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DWORD bytes;
DWORD bytes;
// The magic number 23 in _WSAIOW(IOC_VENDOR, 23) is a Windows-specific vendor IOCTL code
// used to configure TCP immediate ACK behavior (sometimes referred to as TCP_MAXRT).
// This is not a standard IOCTL and is not self-documenting; see Microsoft documentation for details.

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@aljazdu aljazdu Dec 11, 2025

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Added this as a macro on top

if(WSAIoctl(sock, SIO_TCP_SET_ACK_FREQUENCY, &freq, sizeof(freq), NULL, 0, &bytes, NULL, NULL) != 0)
{
mvLog(MVLOG_WARN, "WSAIoctl SIO_TCP_SET_ACK_FREQUENCY could not be set");
}
#endif

#if defined(TCP_QUICKACK)
if(tcpip_setsockopt(sock, IPPROTO_TCP, TCP_QUICKACK, &on, sizeof(on)) < 0)
{
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