Hi Feng,
2016-09-27 12:39 GMT+08:00 <fgao@xxxxxxxxxx>:
> From: Gao Feng <fgao@xxxxxxxxxx>
>
> Current xt_osf codes use memcmp to check if two user fingers are same,
> so it depends on that the struct xt_osf_user_finger is no padding.
> It is one implicit rule, and is not good to maintain.
>
> Now use zero memory and assign the members explicitly.
>
> Signed-off-by: Gao Feng <fgao@xxxxxxxxxx>
> ---
> net/netfilter/xt_osf.c | 32 ++++++++++++++++++++++++++++++--
> 1 file changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/net/netfilter/xt_osf.c b/net/netfilter/xt_osf.c
> index 2455b69..9793670 100644
> --- a/net/netfilter/xt_osf.c
> +++ b/net/netfilter/xt_osf.c
> @@ -61,6 +61,34 @@ static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = {
> [OSF_ATTR_FINGER] = { .len = sizeof(struct xt_osf_user_finger) },
> };
>
> +static void copy_user_finger(struct xt_osf_user_finger *dst,
> + const struct xt_osf_user_finger *src)
> +{
> +#define OSF_COPY_MEMBER(mem) dst->mem = src->mem
> +
> + int i;
> +
> + OSF_COPY_MEMBER(wss.wc);
> + OSF_COPY_MEMBER(wss.val);
> +
> + OSF_COPY_MEMBER(ttl);
> + OSF_COPY_MEMBER(df);
> + OSF_COPY_MEMBER(ss);
> + OSF_COPY_MEMBER(mss);
> + OSF_COPY_MEMBER(opt_num);
> +
> + memcpy(dst->genre, src->genre, sizeof(dst->genre));
> + memcpy(dst->version, src->version, sizeof(dst->version));
> + memcpy(dst->subtype, src->subtype, sizeof(dst->subtype));
> +
> + for (i = 0; i < MAX_IPOPTLEN; ++i) {
> + OSF_COPY_MEMBER(opt[i].kind);
> + OSF_COPY_MEMBER(opt[i].length);
> + OSF_COPY_MEMBER(opt[i].wc.wc);
> + OSF_COPY_MEMBER(opt[i].wc.val);
> + }
> +}
> +
This xt_osf_user_finger{} is carefully designed, no padding now, and
will not be changed in the future, otherwise backward compatibility will
be broken.
I don't think this convert is necessary, actually it is a little ugly, and will
increase the maintenance burden.
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