netdev - Re: [PATCH 09/15] [TCP]: Introduce tcp_hdrlen() and tcp

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Date:	Tue, 13 Mar 2007 16:22:37 -0700
From:	"Jesse Brandeburg" <jesse.brandeburg@...il.com>
To:	"Arnaldo Carvalho de Melo" <acme@...stprotocols.net>
Cc:	"David Miller" <davem@...emloft.net>,
	"Netdev List" <netdev@...r.kernel.org>
Subject: Re: [PATCH 09/15] [TCP]: Introduce tcp_hdrlen() and tcp_optlen()

On 3/13/07, Arnaldo Carvalho de Melo <acme@...stprotocols.net> wrote:
> Introduce tcp_hdrlen() and tcp_optlen():
> The ip_hdrlen() buddy, created to reduce the number of skb->h.th-> uses and to
> avoid the longer, open coded equivalent.

+static inline unsigned int tcp_hdrlen(const struct sk_buff *skb)
+{
+	return skb->h.th->doff * 4;
+}
+
+static inline unsigned int tcp_optlen(const struct sk_buff *skb)
+{
+	return (skb->h.th->doff - 5) * 4;
+}

acme, good stuff, but does the " * 4" generate equivalent assembly
with gcc 3/4 as " << 2" ?

I could assume that the compiler would be smart enough, but every time
I assume I know what the compiler is doing I get myself in trouble.
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