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Patch: Improve HTTP time by sending Connection:close


From: Walter Huf
Subject: Patch: Improve HTTP time by sending Connection:close
Date: Sat, 12 Nov 2016 09:26:17 -0800

GRUB's HTTP module declares support for HTTP/1.1, which defaults to Connection:keepalive. At the end of the content, the server holds the TCP connection open waiting for the next request.
It seems that grub_net_poll_cards() is watching for the HTTP module to set net->stall, and otherwise waits the full 400ms GRUB_NET_INTERVAL to return to processing. However, HTTP module only sets that flag in specific conditions:
If the file is small and takes less than 20 packets, and the server is not using chunked encoding, grub_net_poll_cards() will wait the full 400ms before continuing to process and finish the file download.

This patch sets Connection:close, which will tell the server to close the connection as soon as it has finished sending the file. GRUB closes any connections that are left open (in http_seek), so it does not change performance. When the server disconnects, I think it triggers http_err and then quits out of grub_net_poll_cards early.

---
diff --git a/grub-core/net/http.c b/grub-core/net/http.c
index 5aa4ad3..a5d64f6 100644
--- a/grub-core/net/http.c
+++ b/grub-core/net/http.c
@@ -318,6 +318,7 @@ http_establish (struct grub_file *file, grub_off_t offset, int initial)
    + grub_strlen (data->filename)
    + sizeof (" HTTP/1.1\r\nHost: ") - 1
    + grub_strlen (file->device->net->server)
+   + sizeof ("\r\nConnection: close") - 1
    + sizeof ("\r\nUser-Agent: " PACKAGE_STRING
      "\r\n") - 1
    + sizeof ("Range: bytes=XXXXXXXXXXXXXXXXXXXX"
@@ -366,6 +367,17 @@ http_establish (struct grub_file *file, grub_off_t offset, int initial)
        grub_strlen (file->device->net->server));
 
   ptr = nb->tail;
+  err = grub_netbuff_put (nb,
+  sizeof ("\r\nConnection: close")
+  - 1);
+  if (err)
+    {
+      grub_netbuff_free (nb);
+      return err;
+    }
+  grub_memcpy (ptr, "\r\nConnection: close",
+       sizeof ("\r\nConnection: close") - 1);
+  ptr = nb->tail;
   err = grub_netbuff_put (nb, 
   sizeof ("\r\nUser-Agent: " PACKAGE_STRING "\r\n")
   - 1);


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