[ovs-dev] [PATCH net 1/5] openvswitch: Pad OVS_PACKET_ATTR_PACKET if linear copy was performed

Jesse Gross jesse at nicira.com
Wed Feb 5 06:59:17 UTC 2014

From: Thomas Graf <tgraf at suug.ch>

While the zerocopy method is correctly omitted if user space
does not support unaligned Netlink messages. The attribute is
still not padded correctly as skb_zerocopy() will not ensure
padding and the attribute size is no longer pre calculated
though nla_reserve() which ensured padding previously.

This patch applies appropriate padding if a linear data copy
was performed in skb_zerocopy().

Signed-off-by: Thomas Graf <tgraf at suug.ch>
Acked-by: Zoltan Kiss <zoltan.kiss at citrix.com>
Signed-off-by: Jesse Gross <jesse at nicira.com>
 net/openvswitch/datapath.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index df46928..d1a73a6 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -466,6 +466,14 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 	skb_zerocopy(user_skb, skb, skb->len, hlen);
+	/* Pad OVS_PACKET_ATTR_PACKET if linear copy was performed */
+	if (!(dp->user_features & OVS_DP_F_UNALIGNED)) {
+		size_t plen = NLA_ALIGN(user_skb->len) - user_skb->len;
+		if (plen > 0)
+			memset(skb_put(user_skb, plen), 0, plen);
+	}
 	((struct nlmsghdr *) user_skb->data)->nlmsg_len = user_skb->len;
 	err = genlmsg_unicast(ovs_dp_get_net(dp), user_skb, upcall_info->portid);

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