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Respond to explicit congestion notification (slow down sender)

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This commit is contained in:
Keith Winstein
2012-09-28 19:07:31 -04:00
parent f0d9cb3db3
commit 9ac3b65090
3 changed files with 65 additions and 11 deletions
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src/network/network.cc
+57 -10
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@@ -137,11 +137,20 @@ void Connection::setup( void )
}
#endif
/* set diffserv values to AF42 + ECT */
/* set diffserv values to AF42 + ECT */
uint8_t dscp = 0x92;
if ( setsockopt( sock, IPPROTO_IP, IP_TOS, &dscp, 1) < 0 ) {
// perror( "setsockopt( IP_TOS )" );
}
/* request explicit congestion notification on received datagrams */
#ifdef HAVE_IP_RECVTOS
char tosflag = true;
socklen_t tosoptlen = sizeof( tosflag );
if ( setsockopt( sock, IPPROTO_IP, IP_RECVTOS, &tosflag, tosoptlen ) < 0 ) {
perror( "setsockopt( IP_RECVTOS )" );
}
#endif
}
Connection::Connection( const char *desired_ip, const char *desired_port ) /* server */
@@ -332,26 +341,58 @@ void Connection::send( string s )
string Connection::recv( void )
{
/* receive source address, ECN, and payload in msghdr structure */
struct sockaddr_in packet_remote_addr;
struct msghdr header;
struct iovec msg_iovec;
char buf[ Session::RECEIVE_MTU ];
char msg_payload[ Session::RECEIVE_MTU ];
char msg_control[ Session::RECEIVE_MTU ];
socklen_t addrlen = sizeof( packet_remote_addr );
/* receive source address */
header.msg_name = &packet_remote_addr;
header.msg_namelen = sizeof( packet_remote_addr );
ssize_t received_len = recvfrom( sock, buf, Session::RECEIVE_MTU, 0, (sockaddr *)&packet_remote_addr, &addrlen );
/* receive payload */
msg_iovec.iov_base = msg_payload;
msg_iovec.iov_len = Session::RECEIVE_MTU;
header.msg_iov = &msg_iovec;
header.msg_iovlen = 1;
/* receive explicit congestion notification */
header.msg_control = msg_control;
header.msg_controllen = Session::RECEIVE_MTU;
/* receive flags */
header.msg_flags = 0;
ssize_t received_len = recvmsg( sock, &header, 0 );
if ( received_len < 0 ) {
throw NetworkException( "recvfrom", errno );
}
if ( received_len > Session::RECEIVE_MTU ) {
char buffer[ 2048 ];
snprintf( buffer, 2048, "Received oversize datagram (size %d) and limit is %d\n",
static_cast<int>( received_len ), Session::RECEIVE_MTU );
throw NetworkException( buffer, errno );
if ( header.msg_flags & MSG_TRUNC ) {
throw NetworkException( "Received oversize datagram", errno );
}
Packet p( string( buf, received_len ), &session );
/* receive ECN */
bool congestion_experienced = false;
struct cmsghdr *ecn_hdr = CMSG_FIRSTHDR( &header );
if ( ecn_hdr
&& (ecn_hdr->cmsg_level == IPPROTO_IP)
&& (ecn_hdr->cmsg_type == IP_TOS) ) {
/* got one */
uint8_t *ecn_octet_p = (uint8_t *)CMSG_DATA( ecn_hdr );
assert( ecn_octet_p );
if ( (*ecn_octet_p & 0x03) == 0x03 ) {
congestion_experienced = true;
}
}
Packet p( string( msg_payload, received_len ), &session );
dos_assert( p.direction == (server ? TO_SERVER : TO_CLIENT) ); /* prevent malicious playback to sender */
@@ -362,6 +403,12 @@ string Connection::recv( void )
if ( p.timestamp != uint16_t(-1) ) {
saved_timestamp = p.timestamp;
saved_timestamp_received_at = timestamp();
if ( congestion_experienced ) {
/* signal counterparty to slow down */
/* this will gradually slow the counterparty down to the minimum frame rate */
saved_timestamp -= CONGESTION_TIMESTAMP_PENALTY;
}
}
if ( p.timestamp_reply != uint16_t(-1) ) {