netdev - [PATCH] smsc95xx: Fix tx checksum offload for small packets

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>] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 18 Mar 2010 19:20:10 +0000
From:	Steve Glendinning <steve.glendinning@...c.com>
To:	netdev@...r.kernel.org
Subject: [PATCH] smsc95xx: Fix tx checksum offload for small packets

TX checksum offload does not work properly when transmitting
UDP packets with 0, 1 or 2 bytes of data.  This patch works
around the problem by calculating checksums for these packets
in the driver.

Signed-off-by: Steve Glendinning <steve.glendinning@...c.com>
---
 drivers/net/usb/smsc95xx.c |   18 +++++++++++++++---
 1 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index d222d7e..829963f 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1189,9 +1189,21 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev,
 	}
 
 	if (csum) {
-		u32 csum_preamble = smsc95xx_calc_csum_preamble(skb);
-		skb_push(skb, 4);
-		memcpy(skb->data, &csum_preamble, 4);
+		if (skb->len <= 45) {
+			/* workaround - hardware tx checksum does not work
+			 * properly with extremely small packets */
+			long csstart = skb->csum_start - skb_headroom(skb);
+			__wsum calc = csum_partial(skb->data + csstart,
+				skb->len - csstart, 0);
+			*((__sum16 *)(skb->data + csstart 
+				+ skb->csum_offset)) = csum_fold(calc);
+
+			csum = false;
+		} else {
+			u32 csum_preamble = smsc95xx_calc_csum_preamble(skb);
+			skb_push(skb, 4);
+			memcpy(skb->data, &csum_preamble, 4);
+		}
 	}
 
 	skb_push(skb, 4);
-- 
1.6.6.1

--
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