Disable vlan hw accel when promiscuous mode

2007/11/11, Joonwoo Park <[email protected]>:

Hi,
Not anymore about just e1000 :)
I made an another patch with different approach which doesn't fix nic driver.
In addition, this patch does disable all hw vlan acceleration features (rx, tx, filter) for promiscuous netdevice. (It makes possible tcpdump -i eth0 vlan)
Actually, my previous patch did just disable filter for e1000, so we can't see vlan header of packet. (e1000 stripped off the header)
I think this patch is much better than previous of mine.
How do you think?

Any assist will be appreciated.

Thanks.
Joonwoo

[NET]: Disable vlan hw acceleration when promiscuous mode

---
 include/linux/if_vlan.h |    5 ++-
 net/8021q/vlan.c        |   84 ++++++++++++++++++++++++++++++++++++++++++++---
 net/8021q/vlan.h        |    3 ++
 net/core/dev.c          |    8 ++++-
 4 files changed, 93 insertions(+), 7 deletions(-)

index 976d4b1..b931bee 100644
@@ -63,6 +63,8 @@ struct vlan_hdr {
 
 /* found in socket.c */
 extern void vlan_ioctl_set(int (*hook)(struct net *, void __user *));
+extern void vlan_dev_disable_hwaccel(struct net_device *any_dev);
+void vlan_dev_enable_hwaccel(struct net_device *any_dev);
 
 #define VLAN_NAME "vlan"
 

@@ -367,7 +369,8 @@ static inline int __vlan_hwaccel_get_tag(struct sk_buff *skb, unsigned short *ta
  */
 static inline int vlan_get_tag(struct sk_buff *skb, unsigned short *tag)
 {
-	if (skb->dev->features & NETIF_F_HW_VLAN_TX) {
+	if (skb->dev->features & NETIF_F_HW_VLAN_TX &&
+		!(skb->dev->flags & IFF_PROMISC)) {
 		return __vlan_hwaccel_get_tag(skb, tag);
 	} else {
 		return __vlan_get_tag(skb, tag);

index 2cd1393..e2e10a5 100644
@@ -81,6 +81,9 @@ int unregister_vlan_device(struct net_device *dev);
 int vlan_netlink_init(void);
 void vlan_netlink_fini(void);
 
+void vlan_dev_disable_hwaccel(struct net_device *any_dev);
+void vlan_dev_enable_hwaccel(struct net_device *any_dev);
+
 extern struct rtnl_link_ops vlan_link_ops;
 
 #endif /* !(__BEN_VLAN_802_1Q_INC__) */

index dd7e307..aea35ea 100644
@@ -119,6 +119,7 @@
 #include <linux/err.h>
 #include <linux/ctype.h>
 #include <linux/if_arp.h>
+#include <linux/if_vlan.h>
 
 #include "net-sysfs.h"
 

@@ -2782,8 +2783,13 @@ void dev_set_promiscuity(struct net_device *dev, int inc)
 	unsigned short old_flags = dev->flags;
 
 	__dev_set_promiscuity(dev, inc);
-	if (dev->flags != old_flags)
+	if (dev->flags != old_flags) {
 		dev_set_rx_mode(dev);
+		if (dev->flags & IFF_PROMISC)
+			vlan_dev_disable_hwaccel(dev);
+		else
+			vlan_dev_enable_hwaccel(dev);
+	}
 }
 
 /**

---

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I don't like this :)

Let's not turn promiscuous mode into catch-all flag that disables all optimisations that may interfere with tcpdump. It should show us all the packets by disabling any hardware filtering but that's it.

BTW, how does the VLAN TX acceleration work at all? It's using skb->cb to carry the tags but then calls dev_queue_xmit. Once you do that packet schedulers can scribble all over skb->cb.

Also vlan_skb_recv should be moved out-of-line. It's absolutely humongous. It'll generate tail-calls anyway so performance-wise it's useless.

Cheers,

Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

I have a number of VLAN cleanups queued and intend to do these two changes on top.

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