netdev - Re: [PATCH net-next] net: fix skb_add_data

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Date:	Wed, 6 Apr 2011 21:50:55 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	Wei Yongjun <yjwei@...fujitsu.com>
Cc:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: fix skb_add_data_nocache() to calc csum correctly

Nice catch.

Acked-by: Tom Herbert <therbert@...gle.com>

On Wed, Apr 6, 2011 at 9:40 PM, Wei Yongjun <yjwei@...fujitsu.com> wrote:
> commit c6e1a0d12ca7b4f22c58e55a16beacfb7d3d8462 broken the calc
>  (net: Allow no-cache copy from user on transmit)
> of checksum, which may cause some tcp packets be dropped because
> incorrect checksum. ssh does not work under today's net-next-2.6
> tree.
>
> Signed-off-by: Wei Yongjun <yjwei@...fujitsu.com>
> ---
>  include/net/sock.h |   15 ++++++++-------
>  1 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 43bd515..9cbf23c 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1392,14 +1392,14 @@ static inline void sk_nocaps_add(struct sock *sk, int flags)
>
>  static inline int skb_do_copy_data_nocache(struct sock *sk, struct sk_buff *skb,
>                                           char __user *from, char *to,
> -                                          int copy)
> +                                          int copy, int offset)
>  {
>        if (skb->ip_summed == CHECKSUM_NONE) {
>                int err = 0;
>                __wsum csum = csum_and_copy_from_user(from, to, copy, 0, &err);
>                if (err)
>                        return err;
> -               skb->csum = csum_block_add(skb->csum, csum, skb->len);
> +               skb->csum = csum_block_add(skb->csum, csum, offset);
>        } else if (sk->sk_route_caps & NETIF_F_NOCACHE_COPY) {
>                if (!access_ok(VERIFY_READ, from, copy) ||
>                    __copy_from_user_nocache(to, from, copy))
> @@ -1413,11 +1413,12 @@ static inline int skb_do_copy_data_nocache(struct sock *sk, struct sk_buff *skb,
>  static inline int skb_add_data_nocache(struct sock *sk, struct sk_buff *skb,
>                                       char __user *from, int copy)
>  {
> -       int err;
> +       int err, offset = skb->len;
>
> -       err = skb_do_copy_data_nocache(sk, skb, from, skb_put(skb, copy), copy);
> +       err = skb_do_copy_data_nocache(sk, skb, from, skb_put(skb, copy),
> +                                      copy, offset);
>        if (err)
> -               __skb_trim(skb, skb->len);
> +               __skb_trim(skb, offset);
>
>        return err;
>  }
> @@ -1429,8 +1430,8 @@ static inline int skb_copy_to_page_nocache(struct sock *sk, char __user *from,
>  {
>        int err;
>
> -       err = skb_do_copy_data_nocache(sk, skb, from,
> -                                      page_address(page) + off, copy);
> +       err = skb_do_copy_data_nocache(sk, skb, from, page_address(page) + off,
> +                                      copy, skb->len);
>        if (err)
>                return err;
>
> --
> 1.6.5.2
>
>
>
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