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Advertise a larger MSS to improve TCP performance.

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This commit is contained in:
Michael Brown 2007-01-13 17:36:17 +00:00
parent f11900a9c6
commit 526d314266
2 changed files with 33 additions and 2 deletions
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24
src/include/gpxe/tcp.h
View File

@ -27,6 +27,18 @@ struct tcp_header {
uint16_t urg; /* Urgent pointer */
};
/**
* TCP MSS option
*/
struct tcp_mss_option {
uint8_t kind;
uint8_t length;
uint16_t mss;
};
/** Code for the TCP MSS option */
#define TCP_OPTION_MSS 2
/*
* TCP flags
*/
@ -212,7 +224,17 @@ struct tcp_header {
* guess an arbitrary number that is empirically as large as possible
* while avoiding retransmissions due to dropped packets.
*/
#define TCP_WINDOW_SIZE 2048
#define TCP_WINDOW_SIZE 4096
/**
* Advertised TCP MSS
*
* We currently hardcode this to a reasonable value and hope that the
* sender uses path MTU discovery. The alternative is breaking the
* abstraction layer so that we can find out the MTU from the IP layer
* (which would have to find out from the net device layer).
*/
#define TCP_MSS 1460
/** TCP maximum segment lifetime
*

11
src/net/tcp.c
View File

@ -229,6 +229,8 @@ static int tcp_senddata_conn ( struct tcp_connection *conn, int force_send ) {
struct tcp_application *app = conn->app;
struct pk_buff *pkb;
struct tcp_header *tcphdr;
struct tcp_mss_option *mssopt;
void *payload;
unsigned int flags;
size_t len;
size_t seq_len;
@ -289,13 +291,20 @@ static int tcp_senddata_conn ( struct tcp_connection *conn, int force_send ) {
start_timer ( &conn->timer );
/* Fill up the TCP header */
payload = pkb->data;
if ( flags & TCP_SYN ) {
mssopt = pkb_push ( pkb, sizeof ( *mssopt ) );
mssopt->kind = TCP_OPTION_MSS;
mssopt->length = sizeof ( *mssopt );
mssopt->mss = htons ( TCP_MSS );
}
tcphdr = pkb_push ( pkb, sizeof ( *tcphdr ) );
memset ( tcphdr, 0, sizeof ( *tcphdr ) );
tcphdr->src = conn->local_port;
tcphdr->dest = conn->peer.st_port;
tcphdr->seq = htonl ( conn->snd_seq );
tcphdr->ack = htonl ( conn->rcv_ack );
tcphdr->hlen = ( ( sizeof ( *tcphdr ) / 4 ) << 4 );
tcphdr->hlen = ( ( payload - pkb->data ) << 2 );
tcphdr->flags = flags;
tcphdr->win = htons ( TCP_WINDOW_SIZE );
tcphdr->csum = tcpip_chksum ( pkb->data, pkb_len ( pkb ) );