On Sat, Jan 30, 2016 at 12:48 AM, Josef Bacik <address@hidden> wrote:
Sometimes we have to provision boxes across regions, such as California to
Sweden. The http server has a 10 minute timeout, so if we can't get our 250mb
image transferred fast enough our provisioning fails, which is not ideal. So
add tcp window scaling on open connections and set the window size to 1mb. With
this change we're able to get higher sustained transfers between regions and can
transfer our image in well below 10 minutes. Without this patch we'd time out
every time halfway through the transfer.
RTTM is needed in order to make window scaling work well under heavy congestion
or packet loss. In most cases grub could recover with just window scaling
enabled, but on some machines the congestion would be so high that it would
never recover and would timeout.
I've made the window size configureable with the grub env variable
"tcp_window_size". By default this is set to 1mb but can be configured to
whatever a user wants, and we will calculate the appropriate window size and
scale settings. Thanks,
Please make it net_tcp_window_size to match other net_* variables.
I'm still unsure about increasing it by default. GRUB network
processing is not lightning fast and it looks like it enables partner
on local network to send too much at once which can overflow hardware
receiver buffers. Not sure if this is actually possible.
I hoped DHCP defines standard option for window size but apparently not.
Signed-off-by: Josef Bacik <address@hidden>
---
V1->V2:
-Address Andrei's concerns about making the window size configurable.
-Also make the tcp option stuff more dynamic.
-Add RTTM support to make higher window sizes more stable.
grub-core/net/tcp.c | 141 ++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 132 insertions(+), 9 deletions(-)
diff --git a/grub-core/net/tcp.c b/grub-core/net/tcp.c
index 5da8b11..be5ef30 100644
--- a/grub-core/net/tcp.c
+++ b/grub-core/net/tcp.c
@@ -22,6 +22,7 @@
#include <grub/net/netbuff.h>
#include <grub/time.h>
#include <grub/priority_queue.h>
+#include <grub/env.h>
#define TCP_SYN_RETRANSMISSION_TIMEOUT GRUB_NET_INTERVAL
#define TCP_SYN_RETRANSMISSION_COUNT GRUB_NET_TRIES
@@ -65,6 +66,7 @@ struct grub_net_tcp_socket
grub_uint32_t my_cur_seq;
grub_uint32_t their_start_seq;
grub_uint32_t their_cur_seq;
+ grub_uint32_t cur_tsecr;
grub_uint16_t my_window;
struct unacked *unack_first;
struct unacked *unack_last;
@@ -94,6 +96,8 @@ struct grub_net_tcp_listen
void *hook_data;
};
+#define ALIGNWORD(var) ((var) + 3) & (~3)
+
Can we use ALIGN_UP here?
struct tcphdr
{
grub_uint16_t src;
@@ -106,6 +110,25 @@ struct tcphdr
grub_uint16_t urgent;
} GRUB_PACKED;
+struct tcp_opt
This probably should be tcp_opt_hdr, it is not really complete option.
+{
+ grub_uint8_t kind;
+ grub_uint8_t length;
+} GRUB_PACKED;
+
+struct tcp_scale_opt
+{
+ struct tcp_opt opt;
+ grub_uint8_t scale;
+} GRUB_PACKED;
+
+struct tcp_timestamp_opt
+{
+ struct tcp_opt opt;
+ grub_uint32_t tsval;
+ grub_uint32_t tsecr;
+} GRUB_PACKED;
+
struct tcp_pseudohdr
{
grub_uint32_t src;
@@ -299,9 +322,12 @@ ack_real (grub_net_tcp_socket_t sock, int res)
{
struct grub_net_buff *nb_ack;
struct tcphdr *tcph_ack;
+ struct tcp_timestamp_opt *timestamp;
+ grub_size_t headersize;
grub_err_t err;
- nb_ack = grub_netbuff_alloc (sizeof (*tcph_ack) + 128);
+ headersize = ALIGNWORD(sizeof (*tcph_ack) + sizeof (*timestamp));
+ nb_ack = grub_netbuff_alloc (headersize + 128);
RFC 7323 recommends to use timestamp option only if mutually
negotiated(i.e. both initial SYN and SYN+ACK contain timestamp
option). So it probably should not be done unconditionally.
if (!nb_ack)
return;
err = grub_netbuff_reserve (nb_ack, 128);
@@ -313,7 +339,7 @@ ack_real (grub_net_tcp_socket_t sock, int res)
return;
}
- err = grub_netbuff_put (nb_ack, sizeof (*tcph_ack));
+ err = grub_netbuff_put (nb_ack, headersize);
if (err)
{
grub_netbuff_free (nb_ack);
@@ -322,22 +348,28 @@ ack_real (grub_net_tcp_socket_t sock, int res)
return;
}
tcph_ack = (void *) nb_ack->data;
+ grub_memset (tcph_ack, 0, headersize);
We did not do grub_memset before, why is it necessary now?