Re: [PATCH v1 1/1] l2tp: Use existing macros instead of literal number
From: Guillaume Nault <hidden>
Date: 2016-08-19 01:55:05
On Thu, Aug 18, 2016 at 03:05:19PM +0800, fgao@ikuai8.com wrote:
From: Gao Feng <redacted> 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 <redacted> --- v1: Initial patch
No need to send 'v1' for the initial series.
quoted hunk ↗ jump to hunk
--- 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.
quoted hunk ↗ jump to hunk
@@ -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?
quoted hunk ↗ jump to hunk
/* 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().
quoted hunk ↗ jump to hunk
@@ -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.