Patchwork tun: Optimise handling of bogus gso->hdr_len

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Submitter Herbert Xu
Date June 4, 2009, 11:06 a.m.
Message ID <20090604110600.GA28453@gondor.apana.org.au>
Download mbox | patch
Permalink /patch/28098/
State Accepted
Delegated to: David Miller
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Comments

Herbert Xu - June 4, 2009, 11:06 a.m.
Hi:

tun: Optimise handling of bogus gso->hdr_len

As all current versions of virtio_net generate a value for the
header length that's too small, we should optimise this so that
we don't copy it twice.  This can be done by ensuring that it is
at least as large as the place where we'll write the checksum.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>


Cheers,
David Miller - June 8, 2009, 7:22 a.m.
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Thu, 4 Jun 2009 21:06:00 +1000

> Hi:
> 
> tun: Optimise handling of bogus gso->hdr_len
> 
> As all current versions of virtio_net generate a value for the
> header length that's too small, we should optimise this so that
> we don't copy it twice.  This can be done by ensuring that it is
> at least as large as the place where we'll write the checksum.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Applied.
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Patch

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 735bf41..00d00ad 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -563,6 +563,10 @@  static __inline__ ssize_t tun_get_user(struct tun_struct *tun,
 		if (memcpy_fromiovec((void *)&gso, iv, sizeof(gso)))
 			return -EFAULT;
 
+		if ((gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
+		    gso.csum_start + gso.csum_offset + 2 > gso.hdr_len)
+			gso.hdr_len = gso.csum_start + gso.csum_offset + 2;
+
 		if (gso.hdr_len > len)
 			return -EINVAL;
 	}