From 8e86a32160008b34796f597016cc335680bb3486 Mon Sep 17 00:00:00 2001

From: Josef Bacik <jbacik@fb.com>

Date: Wed, 12 Aug 2015 08:57:55 -0700

Subject: [PATCH 2/3] tcp: add window scaling support

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.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>

---

 grub-core/net/tcp.c | 42 +++++++++++++++++++++++++++++-------------

 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/grub-core/net/tcp.c b/grub-core/net/tcp.c

index fa29a2a..c22ef03 100644

--- a/grub-core/net/tcp.c

+++ b/grub-core/net/tcp.c

@@ -106,6 +106,18 @@ struct tcphdr

   grub_uint16_t urgent;

 } GRUB_PACKED;

+struct tcp_scale_opt {

+  grub_uint8_t kind;

+  grub_uint8_t length;

+  grub_uint8_t scale;

+} GRUB_PACKED;

+

+struct tcp_synhdr {

+  struct tcphdr tcphdr;

+  struct tcp_scale_opt scale_opt;

+  grub_uint8_t padding;

+};

+

 struct tcp_pseudohdr

 {

   grub_uint32_t src;

@@ -555,7 +567,7 @@ grub_net_tcp_open (char *server,

   grub_net_tcp_socket_t socket;

   static grub_uint16_t in_port = 21550;

   struct grub_net_buff *nb;

-  struct tcphdr *tcph;

+  struct tcp_synhdr *tcph;

   int i;

   grub_uint8_t *nbd;

   grub_net_link_level_address_t ll_target_addr;

@@ -617,20 +629,24 @@ grub_net_tcp_open (char *server,

     }

   tcph = (void *) nb->data;

+  grub_memset(tcph, 0, sizeof (*tcph));

   socket->my_start_seq = grub_get_time_ms ();

   socket->my_cur_seq = socket->my_start_seq + 1;

-  socket->my_window = 8192;

-  tcph->seqnr = grub_cpu_to_be32 (socket->my_start_seq);

-  tcph->ack = grub_cpu_to_be32_compile_time (0);

-  tcph->flags = grub_cpu_to_be16_compile_time ((5 << 12) | TCP_SYN);

-  tcph->window = grub_cpu_to_be16 (socket->my_window);

-  tcph->urgent = 0;

-  tcph->src = grub_cpu_to_be16 (socket->in_port);

-  tcph->dst = grub_cpu_to_be16 (socket->out_port);

-  tcph->checksum = 0;

-  tcph->checksum = grub_net_ip_transport_checksum (nb, GRUB_NET_IP_TCP,

-						   &socket->inf->address,

-						   &socket->out_nla);

+  socket->my_window = 32768;

+  tcph->tcphdr.seqnr = grub_cpu_to_be32 (socket->my_start_seq);

+  tcph->tcphdr.ack = grub_cpu_to_be32_compile_time (0);

+  tcph->tcphdr.flags = grub_cpu_to_be16_compile_time ((6 << 12) | TCP_SYN);

+  tcph->tcphdr.window = grub_cpu_to_be16 (socket->my_window);

+  tcph->tcphdr.urgent = 0;

+  tcph->tcphdr.src = grub_cpu_to_be16 (socket->in_port);

+  tcph->tcphdr.dst = grub_cpu_to_be16 (socket->out_port);

+  tcph->tcphdr.checksum = 0;

+  tcph->scale_opt.kind = 3;

+  tcph->scale_opt.length = 3;

+  tcph->scale_opt.scale = 5;

+  tcph->tcphdr.checksum = grub_net_ip_transport_checksum (nb, GRUB_NET_IP_TCP,

+							  &socket->inf->address,

+							  &socket->out_nla);

   tcp_socket_register (socket);

-- 

2.4.3