Xen devel - Feb 2006 - Re: [PATCH] Fix IPSec for Xen checksum offload packets (Jon Mason)

Hello Xen folks,

I have independently verified that this patch indeed fixes the issue (I 
posted a message about the issue over the summer: 
http://lists.xensource.com/archives/html/xen-devel/2005-08/msg00114.html).  
I used changeset 8911 of xen-unstable.hg.  The patch as written expects 
kernel linux-2.6.16-rc2, but changeset 8911 uses kernel 2.6.16-rc4.  I 
verified that the patch works with kernel 2.6.16-rc4.

Cheers,
-Jonathan M. McCune
jonmccune@cmu.edu

>Message: 2
>Date: Mon, 6 Feb 2006 13:43:30 -0600
>From: Jon Mason <jdmason@us.ibm.com>
>Subject: [Xen-devel] [PATCH] Fix IPSec for Xen checksum offload
>	packets
>To: xen-devel@lists.xensource.com
>Cc: dykman@us.ibm.com, jonmccune@cmu.edu
>Message-ID: <20060206194330.GC20904@us.ibm.com>
>Content-Type: text/plain; charset=us-ascii
>
>This patch fixes bug 143 (verified by Jim Dykman).
>
>Thanks,
>Jon
>
>Signed-off-by: James Dykman <dykman@us.ibm.com>
>Signed-off-by: Jon Mason <jdmason@us.ibm.com>
>
># HG changeset patch
># User jdmason@us.ibm.com 
># Node ID 079135b0d58fa0f8f4dc1b9b8ae4baab7d413f47
># Parent  57e6d721842703c08bf7dafbfb5efe3c9a44725d
>
>The Xen checksum offload feature attempts to insert a TCP/UDP 
>checksums into already encrypted packets (esp4) in dom0.  Obviously, 
>it is not possible to insert a checksum into an already encrypted 
>packet, so this patch inserts the checksum prior to encrypting 
>packets.
>
>To do this cleanly, the TCP/UDP header pointers need to be pointed to
>the correct spot, so this functionality has been abstracted into a new
>function.
>
>
>diff -r 57e6d7218427 -r 079135b0d58f linux-2.6-xen-sparse/net/core/dev.c
>--- a/linux-2.6-xen-sparse/net/core/dev.c	Fri Feb  3 18:45:14 2006
>+++ b/linux-2.6-xen-sparse/net/core/dev.c	Mon Feb  6 19:34:52 2006
>@@ -1206,76 +1206,16 @@
> 	return 0;
> }
> 
>-#define HARD_TX_LOCK(dev, cpu) {			\
>-	if ((dev->features & NETIF_F_LLTX) == 0) {	\
>-		spin_lock(&dev->xmit_lock);		\
>-		dev->xmit_lock_owner = cpu;		\
>-	}						\
>-}
>-
>-#define HARD_TX_UNLOCK(dev) {				\
>-	if ((dev->features & NETIF_F_LLTX) == 0) {	\
>-		dev->xmit_lock_owner = -1;		\
>-		spin_unlock(&dev->xmit_lock);		\
>-	}						\
>-}
>-
>-/**
>- *	dev_queue_xmit - transmit a buffer
>- *	@skb: buffer to transmit
>- *
>- *	Queue a buffer for transmission to a network device. The caller must
>- *	have set the device and priority and built the buffer before calling
>- *	this function. The function can be called from an interrupt.
>- *
>- *	A negative errno code is returned on a failure. A success does not
>- *	guarantee the frame will be transmitted as it may be dropped due
>- *	to congestion or traffic shaping.
>- *
>- *
-----------------------------------------------------------------------------------
>- *      I notice this method can also return errors from the queue
disciplines,
>- *      including NET_XMIT_DROP, which is a positive value.  So, errors can
also
>- *      be positive.
>- *
>- *      Regardless of the return value, the skb is consumed, so it is
currently
>- *      difficult to retry a send to this method.  (You can bump the ref
count
>- *      before sending to hold a reference for retry if you are careful.)
>- *
>- *      When calling this method, interrupts MUST be enabled.  This is
because
>- *      the BH enable code must have IRQs enabled so that it will not
deadlock.
>- *          --BLG
>- */
>-
>-int dev_queue_xmit(struct sk_buff *skb)
>-{
>-	struct net_device *dev = skb->dev;
>-	struct Qdisc *q;
>-	int rc = -ENOMEM;
>-
>-	if (skb_shinfo(skb)->frag_list &&
>-	    !(dev->features & NETIF_F_FRAGLIST) &&
>-	    __skb_linearize(skb, GFP_ATOMIC))
>-		goto out_kfree_skb;
>-
>-	/* Fragmented skb is linearized if device does not support SG,
>-	 * or if at least one of fragments is in highmem and device
>-	 * does not support DMA from it.
>-	 */
>-	if (skb_shinfo(skb)->nr_frags &&
>-	    (!(dev->features & NETIF_F_SG) || illegal_highdma(dev, skb))
&&
>-	    __skb_linearize(skb, GFP_ATOMIC))
>-		goto out_kfree_skb;
>-
> #ifdef CONFIG_XEN
>-	/* If a checksum-deferred packet is forwarded to a device that needs a
>-	 * checksum, correct the pointers and force checksumming.
>-	 */
>+int xen_checksum_setup(struct sk_buff *skb)
>+{
> 	if (skb->proto_csum_blank) {
>+		skb->proto_csum_blank = 0;
> 		if (skb->protocol != htons(ETH_P_IP))
>-			goto out_kfree_skb;
>+			goto out;
> 		skb->h.raw = (unsigned char *)skb->nh.iph +
4*skb->nh.iph->ihl;
> 		if (skb->h.raw >= skb->tail)
>-			goto out_kfree_skb;
>+			goto out;
> 		switch (skb->nh.iph->protocol) {
> 		case IPPROTO_TCP:
> 			skb->csum = offsetof(struct tcphdr, check);
>@@ -1284,18 +1224,89 @@
> 			skb->csum = offsetof(struct udphdr, check);
> 			break;
> 		default:
>-			if (net_ratelimit())
>-				printk(KERN_ERR "Attempting to checksum a non-"
>-				       "TCP/UDP packet, dropping a protocol"
>-				       " %d packet", skb->nh.iph->protocol);
>-			rc = -EPROTO;
>-			goto out_kfree_skb;
>+ 			printk(KERN_ERR "Attempting to checksum a non-"
>+ 			       "TCP/UDP packet, dropping a protocol"
>+ 			       " %d packet", skb->nh.iph->protocol);
>+			goto out;
> 		}
> 		if ((skb->h.raw + skb->csum + 2) > skb->tail)
>-			goto out_kfree_skb;
>+			goto out;
> 		skb->ip_summed = CHECKSUM_HW;
> 	}
>+
>+	return 0;
>+out:
>+	return -EPROTO;
>+}
>+#else
>+static inline int xen_checksum_setup(struct sk_buff *skb) {}
> #endif
>+
>+#define HARD_TX_LOCK(dev, cpu) {			\
>+	if ((dev->features & NETIF_F_LLTX) == 0) {	\
>+		spin_lock(&dev->xmit_lock);		\
>+		dev->xmit_lock_owner = cpu;		\
>+	}						\
>+}
>+
>+#define HARD_TX_UNLOCK(dev) {				\
>+	if ((dev->features & NETIF_F_LLTX) == 0) {	\
>+		dev->xmit_lock_owner = -1;		\
>+		spin_unlock(&dev->xmit_lock);		\
>+	}						\
>+}
>+
>+/**
>+ *	dev_queue_xmit - transmit a buffer
>+ *	@skb: buffer to transmit
>+ *
>+ *	Queue a buffer for transmission to a network device. The caller must
>+ *	have set the device and priority and built the buffer before calling
>+ *	this function. The function can be called from an interrupt.
>+ *
>+ *	A negative errno code is returned on a failure. A success does not
>+ *	guarantee the frame will be transmitted as it may be dropped due
>+ *	to congestion or traffic shaping.
>+ *
>+ *
-----------------------------------------------------------------------------------
>+ *      I notice this method can also return errors from the queue
disciplines,
>+ *      including NET_XMIT_DROP, which is a positive value.  So, errors can
also
>+ *      be positive.
>+ *
>+ *      Regardless of the return value, the skb is consumed, so it is
currently
>+ *      difficult to retry a send to this method.  (You can bump the ref
count
>+ *      before sending to hold a reference for retry if you are careful.)
>+ *
>+ *      When calling this method, interrupts MUST be enabled.  This is
because
>+ *      the BH enable code must have IRQs enabled so that it will not
deadlock.
>+ *          --BLG
>+ */
>+
>+int dev_queue_xmit(struct sk_buff *skb)
>+{
>+	struct net_device *dev = skb->dev;
>+	struct Qdisc *q;
>+	int rc = -ENOMEM;
>+
>+	if (skb_shinfo(skb)->frag_list &&
>+	    !(dev->features & NETIF_F_FRAGLIST) &&
>+	    __skb_linearize(skb, GFP_ATOMIC))
>+		goto out_kfree_skb;
>+
>+	/* Fragmented skb is linearized if device does not support SG,
>+	 * or if at least one of fragments is in highmem and device
>+	 * does not support DMA from it.
>+	 */
>+	if (skb_shinfo(skb)->nr_frags &&
>+	    (!(dev->features & NETIF_F_SG) || illegal_highdma(dev, skb))
&&
>+	    __skb_linearize(skb, GFP_ATOMIC))
>+		goto out_kfree_skb;
>+
>+	/* If a checksum-deferred packet is forwarded to a device that needs a
>+	 * checksum, correct the pointers and force checksumming.
>+	 */
>+	if (xen_checksum_setup(skb))
>+		goto out_kfree_skb;
> 
> 	/* If packet is not checksummed and device does not support
> 	 * checksumming for this protocol, complete checksumming here.
>@@ -3350,6 +3361,7 @@
> EXPORT_SYMBOL(net_enable_timestamp);
> EXPORT_SYMBOL(net_disable_timestamp);
> EXPORT_SYMBOL(dev_get_flags);
>+EXPORT_SYMBOL(xen_checksum_setup);
> 
> #if defined(CONFIG_BRIDGE) || defined(CONFIG_BRIDGE_MODULE)
> EXPORT_SYMBOL(br_handle_frame_hook);
>diff -r 57e6d7218427 -r 079135b0d58f patches/linux-2.6.16-rc2/net-csum.patch
>--- a/patches/linux-2.6.16-rc2/net-csum.patch	Fri Feb  3 18:45:14 2006
>+++ b/patches/linux-2.6.16-rc2/net-csum.patch	Mon Feb  6 19:34:52 2006
>@@ -44,3 +44,27 @@
>  	*portptr = newport;
>  	return 1;
>  }
>+--- linux-2.6.16-rc2-xen0/net/ipv4/xfrm4_output.c.orig	2006-02-03
22:36:32.000000000 -0600
>++++ linux-2.6.16-rc2-xen0/net/ipv4/xfrm4_output.c	2006-02-03
22:41:39.000000000 -0600
>+@@ -17,6 +17,8 @@
>+ #include <net/xfrm.h>
>+ #include <net/icmp.h>
>+ 
>++extern int xen_checksum_setup(struct sk_buff *skb);
>++
>+ /* Add encapsulation header.
>+  *
>+  * In transport mode, the IP header will be moved forward to make space
>+@@ -102,7 +104,11 @@ static int xfrm4_output_one(struct sk_bu
>+ 	struct dst_entry *dst = skb->dst;
>+ 	struct xfrm_state *x = dst->xfrm;
>+ 	int err;
>+-	
>++
>++	err = xen_checksum_setup(skb);
>++	if (err)
>++		goto error_nolock;
>++
>+ 	if (skb->ip_summed == CHECKSUM_HW) {
>+ 		err = skb_checksum_help(skb, 0);
>+ 		if (err)
>
>
>
>  
>
>  
>
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