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Subject[PATCH 002 of 3] knfsd: Avoid checksum checks when collecting metadata for a UDP packet.

When recv_msg is called with a size of 0 and MSG_PEEK (and
sunrpc/svcsock.c does), it is clear that we only interested in
metadata (from/to addresses) and not the data, so don't do any
checksum checking at this point. Leave that until the data is
requested.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./net/ipv4/udp.c | 3 +++
./net/ipv6/udp.c | 4 ++++
2 files changed, 7 insertions(+)
diff .prev/net/ipv4/udp.c ./net/ipv4/udp.c
--- .prev/net/ipv4/udp.c 2007-03-02 14:20:13.000000000 +1100
+++ ./net/ipv4/udp.c 2007-03-02 15:13:50.000000000 +1100
@@ -846,6 +846,9 @@ try_again:
goto csum_copy_err;
copy_only = 1;
}
+ if (len == 0 && (flags & MSG_PEEK))
+ /* avoid checksum concerns when just getting metadata */
+ copy_only = 1;

if (copy_only)
err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr),
diff .prev/net/ipv6/udp.c ./net/ipv6/udp.c
--- .prev/net/ipv6/udp.c 2007-03-02 14:20:13.000000000 +1100
+++ ./net/ipv6/udp.c 2007-03-02 15:13:50.000000000 +1100
@@ -151,6 +151,10 @@ try_again:
copy_only = 1;
}

+ if (len == 0 && (flags & MSG_PEEK))
+ /* avoid checksum concerns when just getting metadata */
+ copy_only = 1;
+
if (copy_only)
err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr),
msg->msg_iov, copied );
-
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