netdev - [PATCH net-next 1/3] sunvnet: Do not ask for an ACK for every dring transmit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20140812142724.GH2404@oracle.com>
Date:	Tue, 12 Aug 2014 10:27:24 -0400
From:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:	sowmini.varadhan@...cle.com, davem@...emloft.net,
	raghuram.kothakota@...cle.com
Cc:	netdev@...r.kernel.org
Subject: [PATCH net-next 1/3] sunvnet: Do not ask for an ACK for every dring
 transmit



No need to ask for an ack with every vnet_start_xmit()- the single
ACK with DRING_STOPPED is sufficient for the protocol, and we free
the sk_buff in vnet_start_xmit itself, so we dont need an ACK back.

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@...cle.com>
Acked-by: Raghuram Kothakota <raghuram.kothakota@...cle.com>

---
 drivers/net/ethernet/sun/sunvnet.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c
index d813bfb..b489dd0 100644
--- a/drivers/net/ethernet/sun/sunvnet.c
+++ b/drivers/net/ethernet/sun/sunvnet.c
@@ -691,7 +691,15 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		memset(tx_buf+VNET_PACKET_SKIP+skb->len, 0, len - skb->len);
 	}
 
-	d->hdr.ack = VIO_ACK_ENABLE;
+	/* We don't rely on the ACKs to free the skb in vnet_start_xmit(),
+	 * thus it is safe to not set VIO_ACK_ENABLE for each transmission:
+	 * the protocol itself does not require it as long as the peer
+	 * sends a VIO_SUBTYPE_ACK for VIO_DRING_STOPPED.
+	 *
+	 * An ACK for every packet in the ring is expensive as the
+	 * sending of LDC messages is slow and affects performance.
+	 */
+	d->hdr.ack = VIO_ACK_DISABLE;
 	d->size = len;
 	d->ncookies = port->tx_bufs[dr->prod].ncookies;
 	for (i = 0; i < d->ncookies; i++)
-- 
1.8.4.2

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html