Re: [PATCH 4/6] xen/netback: Always pull through PKT_PROT_LEN bytes into the linear part of an skb.

["Jan Beulich" <JBeulich@novell.com>]

Could you point out what problem this addresses?

Thanks, Jan

>>> Ian Campbell <ian.campbell@citrix.com> 23.02.10 17:47 >>>
Previously PKT_PROT_LEN would only have an effect on the first fragment.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
 drivers/xen/netback/netback.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/drivers/xen/netback/netback.c b/drivers/xen/netback/netback.c
index 7e1dfd1..e668704 100644
--- a/drivers/xen/netback/netback.c
+++ b/drivers/xen/netback/netback.c
@@ -1346,6 +1346,16 @@ static void net_tx_submit(void)
 
 		netbk_fill_frags(skb);
 
+		/*
+		 * If the initial fragment was < PKT_PROT_LEN then
+		 * pull through some bytes from the other fragments to
+		 * increase the linear region to PKT_PROT_LEN bytes.
+		 */
+		if (skb_headlen(skb) < PKT_PROT_LEN && skb_is_nonlinear(skb)) {
+			int target = min_t(int, skb->len, PKT_PROT_LEN);
+			__pskb_pull_tail(skb, target - skb_headlen(skb));
+		}
+
 		skb->dev      = netif->dev;
 		skb->protocol = eth_type_trans(skb, skb->dev);
 
-- 
1.5.6.5


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