l2tp: capture more tx errors in data plane stats

l2tp_xmit_skb has a number of failure paths which are not reflected in
the tunnel and session statistics because the stats are updated by
l2tp_xmit_core.  Hence any errors occurring before l2tp_xmit_core is
called are missed from the statistics.

Refactor the transmit path slightly to capture all error paths.

l2tp_xmit_skb now leaves all the actual work of transmission to
l2tp_xmit_core, and updates the statistics based on l2tp_xmit_core's
return code.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index da66a6e..d2672df 100644 (file)
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -985,56 +985,39 @@ static int l2tp_build_l2tpv3_header(struct l2tp_session *session, void *buf)
        return bufp - optr;
 }
 
-static void l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb, struct flowi *fl)
+/* Queue the packet to IP for output: tunnel socket lock must be held */
+static int l2tp_xmit_queue(struct l2tp_tunnel *tunnel, struct sk_buff *skb, struct flowi *fl)
 {
-       struct l2tp_tunnel *tunnel = session->tunnel;
-       unsigned int len = skb->len;
-       int error;
+       int err;
 
-       /* Queue the packet to IP for output */
        skb->ignore_df = 1;
        skb_dst_drop(skb);
 #if IS_ENABLED(CONFIG_IPV6)
        if (l2tp_sk_is_v6(tunnel->sock))
-               error = inet6_csk_xmit(tunnel->sock, skb, NULL);
+               err = inet6_csk_xmit(tunnel->sock, skb, NULL);
        else
 #endif
-               error = ip_queue_xmit(tunnel->sock, skb, fl);
+               err = ip_queue_xmit(tunnel->sock, skb, fl);
 
-       /* Update stats */
-       if (error >= 0) {
-               atomic_long_inc(&tunnel->stats.tx_packets);
-               atomic_long_add(len, &tunnel->stats.tx_bytes);
-               atomic_long_inc(&session->stats.tx_packets);
-               atomic_long_add(len, &session->stats.tx_bytes);
-       } else {
-               atomic_long_inc(&tunnel->stats.tx_errors);
-               atomic_long_inc(&session->stats.tx_errors);
-       }
+       return err >= 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
 }
 
-/* If caller requires the skb to have a ppp header, the header must be
- * inserted in the skb data before calling this function.
- */
-int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
+static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb)
 {
-       int data_len = skb->len;
        struct l2tp_tunnel *tunnel = session->tunnel;
+       unsigned int data_len = skb->len;
        struct sock *sk = tunnel->sock;
-       struct flowi *fl;
-       struct udphdr *uh;
-       struct inet_sock *inet;
-       int headroom;
-       int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
-       int udp_len;
+       int headroom, uhlen, udp_len;
        int ret = NET_XMIT_SUCCESS;
+       struct inet_sock *inet;
+       struct udphdr *uh;
 
        /* Check that there's enough headroom in the skb to insert IP,
         * UDP and L2TP headers. If not enough, expand it to
         * make room. Adjust truesize.
         */
-       headroom = NET_SKB_PAD + sizeof(struct iphdr) +
-               uhlen + session->hdr_len;
+       uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(*uh) : 0;
+       headroom = NET_SKB_PAD + sizeof(struct iphdr) + uhlen + session->hdr_len;
        if (skb_cow_head(skb, headroom)) {
                kfree_skb(skb);
                return NET_XMIT_DROP;
@@ -1048,8 +1031,7 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
 
        /* Reset skb netfilter state */
        memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
-       IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
-                             IPSKB_REROUTED);
+       IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);
        nf_reset_ct(skb);
 
        bh_lock_sock(sk);
@@ -1069,7 +1051,6 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
        }
 
        inet = inet_sk(sk);
-       fl = &inet->cork.fl;
        switch (tunnel->encap) {
        case L2TP_ENCAPTYPE_UDP:
                /* Setup UDP header */
@@ -1097,12 +1078,34 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
                break;
        }
 
-       l2tp_xmit_core(session, skb, fl);
+       ret = l2tp_xmit_queue(tunnel, skb, &inet->cork.fl);
+
 out_unlock:
        bh_unlock_sock(sk);
 
        return ret;
 }
+
+/* If caller requires the skb to have a ppp header, the header must be
+ * inserted in the skb data before calling this function.
+ */
+int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb)
+{
+       unsigned int len = skb->len;
+       int ret;
+
+       ret = l2tp_xmit_core(session, skb);
+       if (ret == NET_XMIT_SUCCESS) {
+               atomic_long_inc(&session->tunnel->stats.tx_packets);
+               atomic_long_add(len, &session->tunnel->stats.tx_bytes);
+               atomic_long_inc(&session->stats.tx_packets);
+               atomic_long_add(len, &session->stats.tx_bytes);
+       } else {
+               atomic_long_inc(&session->tunnel->stats.tx_errors);
+               atomic_long_inc(&session->stats.tx_errors);
+       }
+       return ret;
+}
 EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
 
 /*****************************************************************************