Le dimanche 14 novembre 2010 Ã 22:35 +0100, Jesper Juhl a Ãcrit :
> By adding two pointer variables to
> net/ipv4/netfilter/ipt_LOG.c::dump_packet() we can save 16 bytes of .text
> and 9 pointer dereferences.
>
> before this patch we did 20 pointer dereferences and had this object file
> size:
> text data bss dec hex filename
> 6233 600 3080 9913 26b9 net/ipv4/netfilter/ipt_LOG.o
>
> after this patch we do just 11 pointer dereferences and have this object
> file size:
> text data bss dec hex filename
> 6217 600 3080 9897 26a9 net/ipv4/netfilter/ipt_LOG.o
>
>
> Please Cc me on replies.
>
>
> Signed-off-by: Jesper Juhl <jj@xxxxxxxxxxxxx>
> ---
> ipt_LOG.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/net/ipv4/netfilter/ipt_LOG.c b/net/ipv4/netfilter/ipt_LOG.c
> index 72ffc8f..02a92de 100644
> --- a/net/ipv4/netfilter/ipt_LOG.c
> +++ b/net/ipv4/netfilter/ipt_LOG.c
> @@ -39,6 +39,8 @@ static void dump_packet(struct sbuff *m,
> struct iphdr _iph;
> const struct iphdr *ih;
> unsigned int logflags;
> + struct sock *sk;
> + struct socket *sk_socket;
>
> if (info->type == NF_LOG_TYPE_LOG)
> logflags = info->u.log.logflags;
> @@ -335,13 +337,15 @@ static void dump_packet(struct sbuff *m,
> }
>
> /* Max length: 15 "UID=4294967295 " */
> - if ((logflags & IPT_LOG_UID) && !iphoff && skb->sk) {
> - read_lock_bh(&skb->sk->sk_callback_lock);
> - if (skb->sk->sk_socket && skb->sk->sk_socket->file)
> + sk = skb->sk;
> + sk_socket = sk->sk_socket;
Really ? sk can be NULL, so you add a NULL dereference.
> + if ((logflags & IPT_LOG_UID) && !iphoff && sk) {
> + read_lock_bh(&sk->sk_callback_lock);
> + if (sk_socket && sk_socket->file)
> sb_add(m, "UID=%u GID=%u ",
> - skb->sk->sk_socket->file->f_cred->fsuid,
> - skb->sk->sk_socket->file->f_cred->fsgid);
> - read_unlock_bh(&skb->sk->sk_callback_lock);
> + sk_socket->file->f_cred->fsuid,
> + sk_socket->file->f_cred->fsgid);
> + read_unlock_bh(&sk->sk_callback_lock);
> }
>
> /* Max length: 16 "MARK=0xFFFFFFFF " */
>
>
>
Most of these "dereferences" are compiler optimized.
You added a bug in your patch, and make ipt_LOG slower if rule is not
asking for IPT_LOG_UID
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