On Thu, Aug 18, 2016 at 03:05:19PM +0800, f...@ikuai8.com wrote:
> From: Gao Feng <f...@ikuai8.com>
>
> 1. Use PPP_ALLSTATIONS/PPP_UI instead of literal 0xff/0x03;
> 2. Use one static const global fixed_ppphdr instead of two same
> static variable ppph in two different functions;
> 3. Use SEND_SHUTDOWN instead of literal 2;
>
> Signed-off-by: Gao Feng <f...@ikuai8.com>
> ---
> v1: Initial patch
No need to send 'v1' for the initial series.
> --- a/net/l2tp/l2tp_ppp.c
> +++ b/net/l2tp/l2tp_ppp.c
> @@ -138,6 +138,8 @@ static const struct ppp_channel_ops pppol2tp_chan_ops = {
>
> static const struct proto_ops pppol2tp_ops;
>
> +static const unsigned char fixed_ppphdr[2] = {PPP_ALLSTATIONS, PPP_UI};
> +
> /* Helpers to obtain tunnel/session contexts from sockets.
> */
> static inline struct l2tp_session *pppol2tp_sock_to_session(struct sock *sk)
> @@ -174,11 +176,11 @@ static int pppol2tp_recv_payload_hook(struct sk_buff
> *skb)
> * Note that skb->data[] isn't dereferenced from a u16 ptr here since
> * the field may be unaligned.
> */
> - if (!pskb_may_pull(skb, 2))
> + if (!pskb_may_pull(skb, sizeof(fixed_ppphdr)))
> return 1;
>
> - if ((skb->data[0] == 0xff) && (skb->data[1] == 0x03))
> - skb_pull(skb, 2);
> + if ((PPP_ADDRESS(skb->data) == PPP_ALLSTATIONS) &&
> (PPP_CONTROL(skb->data) == PPP_UI))
> + skb_pull(skb, sizeof(fixed_ppphdr));
>
Sorry, but I find the original code clearer. It's important to be
explicit about what's done with the sk_buff. Hiding skb->data[x] behind
macros certainly doesn't help.
Same thing for the use of sizeof(fixed_ppphdr) in pskb_may_pull(). The
size of fixed_ppphdr isn't used aftewards, so it's unclear why its size
was pulled. 2 was not a magic number here, it was directly related with
the operations done on the skb (i.e. accessing skb->data[0] and
skb->data[1]). So pskb_may_pull(skb, 2) makes perfect sense.
OTOH, replacing 0xff and 0x03 with PPP_ALLSTATIONS and PPP_UI is fine.
> @@ -312,7 +313,7 @@ static int pppol2tp_sendmsg(struct socket *sock, struct
> msghdr *m,
> error = -ENOMEM;
> skb = sock_wmalloc(sk, NET_SKB_PAD + sizeof(struct iphdr) +
> uhlen + session->hdr_len +
> - sizeof(ppph) + total_len,
> + sizeof(fixed_ppphdr) + total_len,
> 0, GFP_KERNEL);
> if (!skb)
> goto error_put_sess_tun;
> @@ -325,9 +326,9 @@ static int pppol2tp_sendmsg(struct socket *sock, struct
> msghdr *m,
> skb_reserve(skb, uhlen);
>
> /* Add PPP header */
> - skb->data[0] = ppph[0];
> - skb->data[1] = ppph[1];
> - skb_put(skb, 2);
> + PPP_ADDRESS(skb->data) = fixed_ppphdr[0];
> + PPP_CONTROL(skb->data) = fixed_ppphdr[1];
> + skb_put(skb, sizeof(fixed_ppphdr));
>
Same here. What about
+ skb->data[0] = PPP_ALLSTATIONS;
+ skb->data[1] = PPP_UI;
+ skb_put(skb, 2);
and removing ppph entirely?
> /* Copy user data into skb */
> error = memcpy_from_msg(skb_put(skb, total_len), m, total_len);
> @@ -369,7 +370,6 @@ error:
> */
> static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
> {
> - static const u8 ppph[2] = { 0xff, 0x03 };
> struct sock *sk = (struct sock *) chan->private;
> struct sock *sk_tun;
> struct l2tp_session *session;
> @@ -398,14 +398,14 @@ static int pppol2tp_xmit(struct ppp_channel *chan,
> struct sk_buff *skb)
> sizeof(struct iphdr) + /* IP header */
> uhlen + /* UDP header (if L2TP_ENCAPTYPE_UDP) */
> session->hdr_len + /* L2TP header */
> - sizeof(ppph); /* PPP header */
> + sizeof(fixed_ppphdr); /* PPP header */
> if (skb_cow_head(skb, headroom))
> goto abort_put_sess_tun;
>
> /* Setup PPP header */
> - __skb_push(skb, sizeof(ppph));
> - skb->data[0] = ppph[0];
> - skb->data[1] = ppph[1];
> + __skb_push(skb, sizeof(fixed_ppphdr));
> + skb->data[0] = fixed_ppphdr[0];
> + skb->data[1] = fixed_ppphdr[1];
>
Same as for pppol2tp_sendmsg().
> @@ -440,7 +440,7 @@ static void pppol2tp_session_close(struct l2tp_session
> *session)
> BUG_ON(session->magic != L2TP_SESSION_MAGIC);
>
> if (sock) {
> - inet_shutdown(sock, 2);
> + inet_shutdown(sock, SEND_SHUTDOWN);
>
Ok.
