From ea61075c60e6417203bbb5fd54e1f313c99c164c Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Fri, 29 Jun 2012 14:30:18 +0100 Subject: [tcp] Add support for TCP window scaling The maximum unscaled TCP window (64kB) implies a maximum bandwidth of around 300kB/s on a WAN link with an RTT of 200ms. Add support for the TCP window scaling option to remove this upper limit. Signed-off-by: Michael Brown --- src/include/ipxe/tcp.h | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) (limited to 'src/include/ipxe') diff --git a/src/include/ipxe/tcp.h b/src/include/ipxe/tcp.h index 7084af60e..cb3309f2f 100644 --- a/src/include/ipxe/tcp.h +++ b/src/include/ipxe/tcp.h @@ -54,6 +54,31 @@ struct tcp_mss_option { /** Code for the TCP MSS option */ #define TCP_OPTION_MSS 2 +/** TCP window scale option */ +struct tcp_window_scale_option { + uint8_t kind; + uint8_t length; + uint8_t scale; +} __attribute__ (( packed )); + +/** Padded TCP window scale option (used for sending) */ +struct tcp_window_scale_padded_option { + uint8_t nop; + struct tcp_window_scale_option wsopt; +} __attribute (( packed )); + +/** Code for the TCP window scale option */ +#define TCP_OPTION_WS 3 + +/** Advertised TCP window scale + * + * Using a scale factor of 2**9 provides for a maximum window of 32MB, + * which is sufficient to allow Gigabit-speed transfers with a 200ms + * RTT. The minimum advertised window is 512 bytes, which is still + * less than a single packet. + */ +#define TCP_RX_WINDOW_SCALE 9 + /** TCP timestamp option */ struct tcp_timestamp_option { uint8_t kind; @@ -75,7 +100,9 @@ struct tcp_timestamp_padded_option { struct tcp_options { /** MSS option, if present */ const struct tcp_mss_option *mssopt; - /** Timestampe option, if present */ + /** Window scale option, if present */ + const struct tcp_window_scale_option *wsopt; + /** Timestamp option, if present */ const struct tcp_timestamp_option *tsopt; }; @@ -316,6 +343,7 @@ struct tcp_options { ( MAX_LL_NET_HEADER_LEN + \ sizeof ( struct tcp_header ) + \ sizeof ( struct tcp_mss_option ) + \ + sizeof ( struct tcp_window_scale_padded_option ) + \ sizeof ( struct tcp_timestamp_padded_option ) ) /** -- cgit v1.2.3-55-g7522