[Cerowrt-devel] cerowrt-3.6.9-3 test release

[Cerowrt-devel] cerowrt-3.6.9-3 test release

[Dave Taht]

Under absolutely no circumstances try this on your default home
gateway. ipv6 support needs surgery, other tools are in flux...

http://snapon.lab.bufferbloat.net/~cero2/cerowrt/3.6/3.6.9-3/

-- 
Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html

Re: [Cerowrt-devel] cerowrt-3.6.9-3 test release

[Dave Taht]

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Probably the biggest bug in this first attempt: opkg was not included.
This is because the opkg swalker had produced had support for package
signing (in cerowrt 3.3.x), and I didn't port the patches forward...
and then I forgot to include the original opkg in this build!

Felix had reviewed the package signing stuff and felt that it was too
large to use. Certainly part of the opkg signing stuff could be shrunk
(it brings in an unnecessary library), but cutting it as far down as
felix wanted is going to be hard, and worse, doing so will require a
major audit as to the actual security of a non-gpg based signing
system. I'm in a quandary here. Personally I'd prefer to leverage gpg
for package signing, and leverage openssl, which we use anyway.

Also, some new unaligned exception traps have surfaced with ipv6. They
are not bad - only about 1200 on a 60 second rrul test with 24.5/5.5
ceroshaper, but enough to dramatically affect ipv6 latencies, and
affect fq_codel. (see attached)

Aside from that, ad-hoc mode is broken on wifi on either my test box
(iwl x86), or the ar71xx hardware - an interface comes up, associates
with another cell, then fails to transmit packets. I'll be bringing up
another cerowrt box to isolate this today.

I also get utterly dismal performance from same laptop to the router
over wifi, I really am hoping it's the !@#! iwl card, not the
ath9k....

the rrul test (12 netperfs) CAN indeed be run directly to a wndr3800,
but it pays to disable netserver startup from xinetd and run it as a
standalone daemon. It eats an enormous amount of cpu and should only
be used when trying stuff at 100Mbit or less...

Haven't tried the new (BFQ) block I/O scheduler (which might help on
the xinetd startup issue)

On Thu, Dec 6, 2012 at 2:50 PM, Dave Taht <dave.taht@gmail.com> wrote:
> Under absolutely no circumstances try this on your default home
> gateway. ipv6 support needs surgery, other tools are in flux...
>
> http://snapon.lab.bufferbloat.net/~cero2/cerowrt/3.6/3.6.9-3/
>
> --
> Dave Täht
>
> Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html



-- 
Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html

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Re: [Cerowrt-devel] cerowrt-3.6.9-3 test release

[Robert Bradley]

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On 07/12/12 08:20, Dave Taht wrote:
> Also, some new unaligned exception traps have surfaced with ipv6. They
> are not bad - only about 1200 on a 60 second rrul test with 24.5/5.5
> ceroshaper, but enough to dramatically affect ipv6 latencies, and
> affect fq_codel. (see attached)

I have managed to track down possible causes of these new traps now.  
I've noticed that in the IPv6 stack in particular, there's a tendency to 
access the flow label and traffic class fields by casting the header 
structure to __be32*.  Needless to say, this ends up producing a lot of 
unaligned access traps.

There's a possible issue with setting the IPv6 ECN bits, but that should 
also affect the Sugarland build too.  There's also a few *(__be32*) 
dereferences in net/ipv6/ip6_route.c and net/ipv6/ip6_tunnel.c that are 
new to the 3.6 kernel.  The attached patches should hopefully fix all of 
the new traps.

-- 
Robert Bradley


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diff --git a/include/net/inet_ecn.h b/include/net/inet_ecn.h
index 2fa1469..0b6a7fd 100644
--- a/include/net/inet_ecn.h
+++ b/include/net/inet_ecn.h
@@ -111,15 +111,21 @@ struct ipv6hdr;
 
 static inline int IP6_ECN_set_ce(struct ipv6hdr *iph)
 {
+	__be32 dsfield;
 	if (INET_ECN_is_not_ect(ipv6_get_dsfield(iph)))
 		return 0;
-	*(__be32*)iph |= htonl(INET_ECN_CE << 20);
+	dsfield = __get_unaligned_cpu32((__be32*)iph);
+	dsfield |= htonl(INET_ECN_CE << 20);
+	__put_unaligned_cpu32(dsfield, (__be32*)iph);
 	return 1;
 }
 
 static inline void IP6_ECN_clear(struct ipv6hdr *iph)
 {
-	*(__be32*)iph &= ~htonl(INET_ECN_MASK << 20);
+	__be32 dsfield;
+	dsfield = __get_unaligned_cpu32((__be32*)iph);
+	dsfield &= ~htonl(INET_ECN_MASK << 20);
+	__put_unaligned_cpu32(dsfield, (__be32*)iph);
 }
 
 static inline void ipv6_copy_dscp(unsigned int dscp, struct ipv6hdr *inner)

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diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 19e7aa0..6cbd2b7 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -492,7 +492,7 @@ int datagram_recv_ctl(struct sock *sk, struct msghdr *msg, struct sk_buff *skb)
 		put_cmsg(msg, SOL_IPV6, IPV6_TCLASS, sizeof(tclass), &tclass);
 	}
 
-	if (np->rxopt.bits.rxflow && (*(__be32 *)nh & IPV6_FLOWINFO_MASK)) {
+	if (np->rxopt.bits.rxflow && (__get_unaligned_cpu32((__be32 *)nh) & IPV6_FLOWINFO_MASK)) {
 		__be32 flowinfo = __get_unaligned_cpu32((__be32 *)nh) & IPV6_FLOWINFO_MASK;
 		put_cmsg(msg, SOL_IPV6, IPV6_FLOWINFO, sizeof(flowinfo), &flowinfo);
 	}
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 5b2d63e..b6689e3 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -221,7 +221,9 @@ int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 	if (hlimit < 0)
 		hlimit = ip6_dst_hoplimit(dst);
 
-	*(__be32 *)hdr = htonl(0x60000000 | (tclass << 20)) | fl6->flowlabel;
+	__put_unaligned_cpu32(htonl(0x60000000 | (tclass << 20))
+			      | fl6->flowlabel,
+		              (__be32*)hdr);
 
 	hdr->payload_len = htons(seg_len);
 	hdr->nexthdr = proto;
@@ -272,7 +274,7 @@ int ip6_nd_hdr(struct sock *sk, struct sk_buff *skb, struct net_device *dev,
 	skb_put(skb, sizeof(struct ipv6hdr));
 	hdr = ipv6_hdr(skb);
 
-	*(__be32*)hdr = htonl(0x60000000);
+	__put_unaligned_cpu32(htonl(0x60000000), (__be32*)hdr);
 
 	hdr->payload_len = htons(len);
 	hdr->nexthdr = proto;
@@ -1635,8 +1637,9 @@ int ip6_push_pending_frames(struct sock *sk)
 	skb_reset_network_header(skb);
 	hdr = ipv6_hdr(skb);
 
-	*(__be32*)hdr = fl6->flowlabel |
-		     htonl(0x60000000 | ((int)np->cork.tclass << 20));
+	__put_unaligned_cpu32(fl6->flowlabel |
+			      htonl(0x60000000 | ((int)np->cork.tclass << 20)),
+			      (__be32*)hdr);
 
 	hdr->hop_limit = np->cork.hop_limit;
 	hdr->nexthdr = proto;
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 9a1d5fe..455ea7f 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -997,7 +997,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
 	skb_push(skb, sizeof(struct ipv6hdr));
 	skb_reset_network_header(skb);
 	ipv6h = ipv6_hdr(skb);
-	*(__be32*)ipv6h = fl6->flowlabel | htonl(0x60000000);
+	__put_unaligned_cpu32(fl6->flowlabel | htonl(0x60000000), (__be32*)ipv6h);
 	dsfield = INET_ECN_encapsulate(0, dsfield);
 	ipv6_change_dsfield(ipv6h, ~INET_ECN_MASK, dsfield);
 	ipv6h->hop_limit = t->parms.hop_limit;
@@ -1103,9 +1103,9 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	dsfield = ipv6_get_dsfield(ipv6h);
 	if (t->parms.flags & IP6_TNL_F_USE_ORIG_TCLASS)
-		fl6.flowlabel |= (*(__be32 *) ipv6h & IPV6_TCLASS_MASK);
+		fl6.flowlabel |= (__get_unaligned_cpu32((__be32 *) ipv6h) & IPV6_TCLASS_MASK);
 	if (t->parms.flags & IP6_TNL_F_USE_ORIG_FLOWLABEL)
-		fl6.flowlabel |= (*(__be32 *) ipv6h & IPV6_FLOWLABEL_MASK);
+		fl6.flowlabel |= (__get_unaligned_cpu32((__be32 *) ipv6h) & IPV6_FLOWLABEL_MASK);
 	if (t->parms.flags & IP6_TNL_F_USE_ORIG_FWMARK)
 		fl6.flowi6_mark = skb->mark;
 
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3e350eb..c2787a1 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1117,7 +1117,7 @@ void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,
 	fl6.flowi6_flags = 0;
 	fl6.daddr = iph->daddr;
 	fl6.saddr = iph->saddr;
-	fl6.flowlabel = (*(__be32 *) iph) & IPV6_FLOWINFO_MASK;
+	fl6.flowlabel = __get_unaligned_cpu32((__be32 *) iph) & IPV6_FLOWINFO_MASK;
 
 	dst = ip6_route_output(net, NULL, &fl6);
 	if (!dst->error)
@@ -1145,7 +1145,7 @@ void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark)
 	fl6.flowi6_flags = 0;
 	fl6.daddr = iph->daddr;
 	fl6.saddr = iph->saddr;
-	fl6.flowlabel = (*(__be32 *) iph) & IPV6_FLOWINFO_MASK;
+	fl6.flowlabel = __get_unaligned_cpu32((__be32 *) iph) & IPV6_FLOWINFO_MASK;
 
 	dst = ip6_route_output(net, NULL, &fl6);
 	if (!dst->error)