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

[Robert Bradley <robert.bradley1@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 922 bytes --]

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


[-- Attachment #2: 924-ecn-alignment-fixes.patch --]
[-- Type: text/x-patch, Size: 871 bytes --]

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)

[-- Attachment #3: 925-ipv6-alignment-fixes.patch --]
[-- Type: text/x-patch, Size: 3949 bytes --]

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)