Re: regression: tethering fails in 3.5 with iwlwifi

5 messages, 4 authors, 2012-09-21 · open the first message on its own page

Re: regression: tethering fails in 3.5 with iwlwifi

From: Eric Dumazet <hidden>
Date: 2012-09-20 13:04:50

Try to pull 40 bytes : Thats OK for tcp performance, because 40 bytes
is the minimum size of IP+TCP headers

pskb_may_pull(skb, 40);

(instead of your  skb_linearize(skb);)


On Thu, Sep 20, 2012 at 2:58 PM, Artem Bityutskiy
[off-list ref] wrote:

quoted hunk

On Thu, 2012-09-20 at 14:45 +0200, Eric Dumazet wrote:

quoted

I guess you only need to make sure 14 bytes of ethernet header are
available before eth_type_trans(skb, dev);

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 61c621e..ffe5f84 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c

@@ -1795,9 +1795,13 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)

                if (skb) {
                        /* deliver to local stack */
-                       skb->protocol = eth_type_trans(skb, dev);
-                       memset(skb->cb, 0, sizeof(skb->cb));
-                       netif_receive_skb(skb);
+                       if (pskb_may_pull(skb, sizeof(struct ethhdr))) {
+                               skb->protocol = eth_type_trans(skb, dev);
+                               memset(skb->cb, 0, sizeof(skb->cb));
+                               netif_receive_skb(skb);
+                       } else {
+                               kfree_skb(skb);
+                       }
                }
        }

Does not help, this one does:

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 61c621e..6888586 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c

@@ -1797,6 +1797,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
                        /* deliver to local stack */
                        skb->protocol = eth_type_trans(skb, dev);
                        memset(skb->cb, 0, sizeof(skb->cb));
+                       skb_linearize(skb);
                        netif_receive_skb(skb);
                }

--

Best Regards,
Artem Bityutskiy

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Re: regression: tethering fails in 3.5 with iwlwifi

From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Date: 2012-09-20 13:17:35

On Thu, 2012-09-20 at 15:04 +0200, Eric Dumazet wrote:

Try to pull 40 bytes : Thats OK for tcp performance, because 40 bytes
is the minimum size of IP+TCP headers

pskb_may_pull(skb, 40);

OK, I've tried almost this (see below) and it solves my issue:

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 965e6ec..7f079d0 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c

@@ -1798,9 +1798,13 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 
                if (skb) {
                        /* deliver to local stack */
-                       skb->protocol = eth_type_trans(skb, dev);
-                       memset(skb->cb, 0, sizeof(skb->cb));
-                       netif_receive_skb(skb);
+                       if (pskb_may_pull(skb, 40)) {
+                               skb->protocol = eth_type_trans(skb, dev);
+                               memset(skb->cb, 0, sizeof(skb->cb));
+                               netif_receive_skb(skb);
+                       } else {
+                               kfree_skb(skb);
+                       }
                }
        }

-- 
Best Regards,
Artem Bityutskiy

Re: regression: tethering fails in 3.5 with iwlwifi

From: Eric Dumazet <hidden>
Date: 2012-09-20 13:22:08

On Thu, 2012-09-20 at 16:22 +0300, Artem Bityutskiy wrote:

quoted hunk

OK, I've tried almost this (see below) and it solves my issue:

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 965e6ec..7f079d0 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c

@@ -1798,9 +1798,13 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 
                if (skb) {
                        /* deliver to local stack */
-                       skb->protocol = eth_type_trans(skb, dev);
-                       memset(skb->cb, 0, sizeof(skb->cb));
-                       netif_receive_skb(skb);
+                       if (pskb_may_pull(skb, 40)) {
+                               skb->protocol = eth_type_trans(skb, dev);
+                               memset(skb->cb, 0, sizeof(skb->cb));
+                               netif_receive_skb(skb);
+                       } else {
+                               kfree_skb(skb);
+                       }
                }
        }

OK but you cant do that, or small frames will be dropped.

Anyway its a hack, we should find the buggy layer.

You could use dropwatch (drop_monitor) to check where frame is dropped.

modprobe drop_monitor
dropwatch -l kas

Re: regression: tethering fails in 3.5 with iwlwifi

From: Eric Dumazet <hidden>
Date: 2012-09-20 14:25:54

On Thu, 2012-09-20 at 16:22 +0300, Artem Bityutskiy wrote:

quoted hunk

On Thu, 2012-09-20 at 15:04 +0200, Eric Dumazet wrote:

quoted

Try to pull 40 bytes : Thats OK for tcp performance, because 40 bytes
is the minimum size of IP+TCP headers

pskb_may_pull(skb, 40);

OK, I've tried almost this (see below) and it solves my issue:

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 965e6ec..7f079d0 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c

@@ -1798,9 +1798,13 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 
                if (skb) {
                        /* deliver to local stack */
-                       skb->protocol = eth_type_trans(skb, dev);
-                       memset(skb->cb, 0, sizeof(skb->cb));
-                       netif_receive_skb(skb);
+                       if (pskb_may_pull(skb, 40)) {
+                               skb->protocol = eth_type_trans(skb, dev);
+                               memset(skb->cb, 0, sizeof(skb->cb));
+                               netif_receive_skb(skb);
+                       } else {
+                               kfree_skb(skb);
+                       }
                }
        }

Please remove this hack and try the following bugfix in raw handler

icmp_filter() should not modify skb, or else its caller should not
assume ip_hdr() is unchanged.

 net/ipv4/raw.c |   29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index f242578..3fa8c96 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c

@@ -128,25 +128,30 @@ found:
 }
 
 /*
- *	0 - deliver
- *	1 - block
+ *	false - deliver
+ *	true - block
  */
-static __inline__ int icmp_filter(struct sock *sk, struct sk_buff *skb)
+static bool icmp_filter(struct sock *sk, const struct sk_buff *skb)
 {
-	int type;
-
-	if (!pskb_may_pull(skb, sizeof(struct icmphdr)))
-		return 1;
-
-	type = icmp_hdr(skb)->type;
-	if (type < 32) {
+	__u8 _type;
+	const __u8 *type;
+
+	type = skb_header_pointer(skb,
+				  skb_transport_offset(skb) +
+				  offsetof(struct icmphdr, type),
+				  sizeof(_type),
+				  &_type);
+	if (!type)
+		return true;
+
+	if (*type < 32) {
 		__u32 data = raw_sk(sk)->filter.data;
 
-		return ((1 << type) & data) != 0;
+		return ((1U << *type) & data) != 0;
 	}
 
 	/* Do not block unknown ICMP types */
-	return 0;
+	return false;
 }
 
 /* IP input processing comes here for RAW socket delivery.

Re: regression: tethering fails in 3.5 with iwlwifi

From: David Miller <hidden>
Date: 2012-09-21 17:24:45

From: Eric Dumazet <redacted>
Date: Thu, 20 Sep 2012 16:25:49 +0200

Please remove this hack and try the following bugfix in raw handler

icmp_filter() should not modify skb, or else its caller should not
assume ip_hdr() is unchanged.

Right, good catch.

Please submit this fix formally Eric, thanks a lot.
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