netdev - Re: [PATCH net-next v3 1/3] flow_dissector: factor out the ports extraction in skb_flow_get

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Date:	Thu, 26 Sep 2013 16:36:31 +0200
From:	Veaceslav Falico <vfalico@...hat.com>
To:	Nikolay Aleksandrov <nikolay@...hat.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, andy@...yhouse.net,
	fubar@...ibm.com, eric.dumazet@...il.com
Subject: Re: [PATCH net-next v3 1/3] flow_dissector: factor out the ports
 extraction in skb_flow_get_ports

On Thu, Sep 26, 2013 at 04:09:40PM +0200, Nikolay Aleksandrov wrote:
>Factor out the code that extracts the ports from skb_flow_dissect and
>add a new function skb_flow_get_ports which can be re-used.
>
>Suggested-by: Veaceslav Falico <vfalico@...hat.com>
>Signed-off-by: Nikolay Aleksandrov <nikolay@...hat.com>

Reviewed-by: Veaceslav Falico <vfalico@...hat.com>

>---
>v2: new patch
>v3: fix a bug in skb_flow_dissect where thoff didn't have poff added by
>    modifying thoff directly in skb_flow_get_ports as it's done anyway.
>    Also add the necessary export symbol for skb_flow_get_ports.
>This seems like a good idea because there're other users that can re-use
>it later as well.
>
> include/net/flow_keys.h   |  1 +
> net/core/flow_dissector.c | 41 ++++++++++++++++++++++++++++++-----------
> 2 files changed, 31 insertions(+), 11 deletions(-)
>
>diff --git a/include/net/flow_keys.h b/include/net/flow_keys.h
>index ac2439d..4db84ae 100644
>--- a/include/net/flow_keys.h
>+++ b/include/net/flow_keys.h
>@@ -14,4 +14,5 @@ struct flow_keys {
> };
>
> bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow);
>+__be32 skb_flow_get_ports(const struct sk_buff *skb, int *thoff, u8 ip_proto);
> #endif
>diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
>index 1929af8..7785398 100644
>--- a/net/core/flow_dissector.c
>+++ b/net/core/flow_dissector.c
>@@ -25,9 +25,37 @@ static void iph_to_flow_copy_addrs(struct flow_keys *flow, const struct iphdr *i
> 	memcpy(&flow->src, &iph->saddr, sizeof(flow->src) + sizeof(flow->dst));
> }
>
>+/**
>+ * skb_flow_get_ports - extract the upper layer ports and return them
>+ * @skb: buffer to extract the ports from
>+ * @thoff: pointer to transport header offset
>+ * @ip_proto: protocol for which to get port offset
>+ *
>+ * The function will try to retrieve the ports at offset thoff + poff where poff
>+ * is the protocol port offset returned from proto_ports_offset, and if poff is
>+ * more than or equal to 0 it'll add it to the value at the thoff address
>+ */
>+__be32 skb_flow_get_ports(const struct sk_buff *skb, int *thoff, u8 ip_proto)
>+{
>+	int poff = proto_ports_offset(ip_proto);
>+
>+	if (poff >= 0) {
>+		__be32 *ports, _ports;
>+
>+		*thoff += poff;
>+		ports = skb_header_pointer(skb, *thoff, sizeof(_ports),
>+					   &_ports);
>+		if (ports)
>+			return *ports;
>+	}
>+
>+	return 0;
>+}
>+EXPORT_SYMBOL(skb_flow_get_ports);
>+
> bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
> {
>-	int poff, nhoff = skb_network_offset(skb);
>+	int nhoff = skb_network_offset(skb);
> 	u8 ip_proto;
> 	__be16 proto = skb->protocol;
>
>@@ -150,16 +178,7 @@ ipv6:
> 	}
>
> 	flow->ip_proto = ip_proto;
>-	poff = proto_ports_offset(ip_proto);
>-	if (poff >= 0) {
>-		__be32 *ports, _ports;
>-
>-		nhoff += poff;
>-		ports = skb_header_pointer(skb, nhoff, sizeof(_ports), &_ports);
>-		if (ports)
>-			flow->ports = *ports;
>-	}
>-
>+	flow->ports = skb_flow_get_ports(skb, &nhoff, ip_proto);
> 	flow->thoff = (u16) nhoff;
>
> 	return true;
>-- 
>1.8.1.4
>
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