53 lines
2.1 KiB
Diff
53 lines
2.1 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Javier Martinez Canillas <javierm@redhat.com>
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Date: Thu, 20 Aug 2020 13:19:00 +0200
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Subject: [PATCH] tftp: increase blocksize from 1024 to 1428 octets
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The RFC2348 [0] defines how the TFTP Blocksize Option should be negotiated
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between the client and the server. GRUB just hardcodes this to 1024, which
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limits the maximum file size to be downloaded to 67107840 byes, since the
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block number is stored in a 16-bit field.
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This limit is a problem when attempting to fetch large files (i.e: initrd
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images) because the block number will overflow, and GRUB will never ack a
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packet. This causes a timeout when trying to download the file over TFTP.
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Since the TFTP support in GRUB is used primarily to fetch the kernel and
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initrd images, let's bump the blocksize to 1428 which would allow to get
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larger files.
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The value of 1428 is chosen to increase the maximum file size limit, while
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avoiding IP packet fragmentation which could be a problem in some networks.
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The TFTP support should be improved to define the blocksize dynamically
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instead of hardcoding it, but until that happens is better to use a value
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that at least allows to fetch kernel and initrd images with the sizes that
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are present in the install media that is used for network booting.
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[0]: https://tools.ietf.org/html/rfc2348
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Resolves: rhbz#1869335
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Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
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---
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grub-core/net/tftp.c | 6 +++---
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1 file changed, 3 insertions(+), 3 deletions(-)
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diff --git a/grub-core/net/tftp.c b/grub-core/net/tftp.c
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index 22badd74316..43920885411 100644
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--- a/grub-core/net/tftp.c
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+++ b/grub-core/net/tftp.c
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@@ -322,9 +322,9 @@ tftp_open (struct grub_file *file, const char *filename)
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rrqlen += grub_strlen ("blksize") + 1;
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rrq += grub_strlen ("blksize") + 1;
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- grub_strcpy (rrq, "1024");
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- rrqlen += grub_strlen ("1024") + 1;
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- rrq += grub_strlen ("1024") + 1;
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+ grub_strcpy (rrq, "1428");
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+ rrqlen += grub_strlen ("1428") + 1;
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+ rrq += grub_strlen ("1428") + 1;
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grub_strcpy (rrq, "tsize");
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rrqlen += grub_strlen ("tsize") + 1;
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