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IPv6 QoS fix #3622

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IPv6 QoS fix #3622

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bdd65af
Correct data size for IPV6_TCLASS
Feb 7, 2026
e39af2d
Add error checking for setsockopt()
softins Feb 8, 2026
a647941
Correct data size for IPV6_V6ONLY
softins Feb 8, 2026
6de1d02
Also need setsockopt() for IPv4 on a dual-proto socket
softins Feb 8, 2026
b5a38db
Remove socket options that do not work on Windows and Apple
softins Feb 9, 2026
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31 changes: 25 additions & 6 deletions src/socket.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -114,12 +114,28 @@ void CSocket::Init ( const quint16 iNewPortNumber, const quint16 iNewQosNumber,

// The IPV6_V6ONLY socket option must be false in order for the socket to listen on both protocols.
// On Linux it's false by default on most (all?) distros, but on Windows it is true by default
const uint8_t no = 0;
setsockopt ( UdpSocket, IPPROTO_IPV6, IPV6_V6ONLY, (const char*) &no, sizeof ( no ) );
const int no = 0;
if ( setsockopt ( UdpSocket, IPPROTO_IPV6, IPV6_V6ONLY, (const char*) &no, sizeof ( no ) ) == -1 )
{
throw CGenErr ( "setsockopt for IPV6_V6ONLY failed", "Network Error" );
}

// set the QoS
const char tos = (char) iQosNumber; // Quality of Service
setsockopt ( UdpSocket, IPPROTO_IPV6, IPV6_TCLASS, &tos, sizeof ( tos ) );
const int tos = (int) iQosNumber; // Quality of Service
#if !defined( Q_OS_WIN )
if ( setsockopt ( UdpSocket, IPPROTO_IPV6, IPV6_TCLASS, (const char*) &tos, sizeof ( tos ) ) == -1 )
{
throw CGenErr ( "setsockopt for IPV6_TCLASS failed", "Network Error" );
}
#endif

#if !defined( Q_OS_DARWIN )
// set the QoS for IPv4 as well, as this is a dual-protocol socket
if ( setsockopt ( UdpSocket, IPPROTO_IP, IP_TOS, (const char*) &tos, sizeof ( tos ) ) == -1 )
{
throw CGenErr ( "setsockopt for IP_TOS failed", "Network Error" );
}
#endif

UdpSocketAddr.sa6.sin6_family = AF_INET6;
UdpSocketAddr.sa6.sin6_addr = in6addr_any;
Expand Down Expand Up @@ -147,8 +163,11 @@ void CSocket::Init ( const quint16 iNewPortNumber, const quint16 iNewQosNumber,
}

// set the QoS
const char tos = (char) iQosNumber; // Quality of Service
setsockopt ( UdpSocket, IPPROTO_IP, IP_TOS, &tos, sizeof ( tos ) );
const int tos = (int) iQosNumber; // Quality of Service
if ( setsockopt ( UdpSocket, IPPROTO_IP, IP_TOS, (const char*) &tos, sizeof ( tos ) ) == -1 )
{
throw CGenErr ( "setsockopt for IP_TOS failed", "Network Error" );
}

// preinitialize socket in address (only the port number is missing)
UdpSocketAddr.sa4.sin_family = AF_INET;
Expand Down