Jan Beulich
2010-Dec-17 09:42 UTC
[Xen-devel] [PATCH] linux-2.6.18/netback: Always pull through PKT_PROT_LEN bytes into the linear part of an skb
From: Ian Campbell <ian.campbell@citrix.com>
Subject: xen/netback: Always pull through PKT_PROT_LEN bytes into the linear
part of an skb
Previously PKT_PROT_LEN would only have an effect on the first
fragment.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
From: Steven Smith <ssmith@xensource.com>
Subject: xen/netback: try to pull a minimum of 72 bytes into the skb data area
... when receiving a packet into netback. The previous number, 64,
tended to place a fragment boundary in the middle of the TCP header
options and led to unnecessary fragmentation in Windows <-> Windows
networking.
From: Paul Durrant <paul.durrant@citrix.com>
Subject: Re-define PKT_PROT_LEN to be bigger.
Re-define PKT_PROT_LEN to be big enough to handle maximal IPv4 and TCP
options and phrase the definition so that it''s reasonably obvious
that''s what it''s for.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@novell.com>
--- sle10sp4-2010-12-15.orig/drivers/xen/netback/netback.c
+++ sle10sp4-2010-12-15/drivers/xen/netback/netback.c
@@ -35,6 +35,8 @@
*/
#include "common.h"
+#include <linux/if_vlan.h>
+#include <linux/tcp.h>
#include <xen/balloon.h>
#include <xen/interface/memory.h>
@@ -105,7 +107,14 @@ static inline int netif_page_index(struc
return idx;
}
-#define PKT_PROT_LEN 64
+/*
+ * This is the amount of packet we copy rather than map, so that the
+ * guest can''t fiddle with the contents of the headers while we do
+ * packet processing on them (netfilter, routing, etc).
+ */
+#define PKT_PROT_LEN (ETH_HLEN + VLAN_HLEN + \
+ sizeof(struct iphdr) + MAX_IPOPTLEN + \
+ sizeof(struct tcphdr) + 40 /* MAX_TCP_OPTION_SPACE */)
static struct pending_tx_info {
netif_tx_request_t req;
@@ -1458,6 +1467,16 @@ static void net_tx_action(unsigned long
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);
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