net: introduce rx_handler results and logic around that

This patch allows rx_handlers to better signalize what to do next to
it's caller. That makes skb->deliver_no_wcard no longer needed.

kernel-doc for rx_handler_result is taken from Nicolas' patch.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Reviewed-by: Nicolas de Pesloüan <nicolas.2p.debian@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 04119b1..27c413a 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1480,20 +1480,23 @@ static bool bond_should_deliver_exact_match(struct sk_buff *skb,
        return false;
 }
 
-static struct sk_buff *bond_handle_frame(struct sk_buff *skb)
+static rx_handler_result_t bond_handle_frame(struct sk_buff **pskb)
 {
+       struct sk_buff *skb = *pskb;
        struct slave *slave;
        struct net_device *bond_dev;
        struct bonding *bond;
 
-       skb = skb_share_check(skb, GFP_ATOMIC);
-       if (unlikely(!skb))
-               return NULL;
-
        slave = bond_slave_get_rcu(skb->dev);
        bond_dev = ACCESS_ONCE(slave->dev->master);
        if (unlikely(!bond_dev))
-               return skb;
+               return RX_HANDLER_PASS;
+
+       skb = skb_share_check(skb, GFP_ATOMIC);
+       if (unlikely(!skb))
+               return RX_HANDLER_CONSUMED;
+
+       *pskb = skb;
 
        bond = netdev_priv(bond_dev);
 
@@ -1501,8 +1504,7 @@ static struct sk_buff *bond_handle_frame(struct sk_buff *skb)
                slave->dev->last_rx = jiffies;
 
        if (bond_should_deliver_exact_match(skb, slave, bond)) {
-               skb->deliver_no_wcard = 1;
-               return skb;
+               return RX_HANDLER_EXACT;
        }
 
        skb->dev = bond_dev;
@@ -1514,12 +1516,12 @@ static struct sk_buff *bond_handle_frame(struct sk_buff *skb)
                if (unlikely(skb_cow_head(skb,
                                          skb->data - skb_mac_header(skb)))) {
                        kfree_skb(skb);
-                       return NULL;
+                       return RX_HANDLER_CONSUMED;
                }
                memcpy(eth_hdr(skb)->h_dest, bond_dev->dev_addr, ETH_ALEN);
        }
 
-       return skb;
+       return RX_HANDLER_ANOTHER;
 }
 
 /* enslave device <slave> to bond device <master> */

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 497991b..5b37d3c 100644 (file)
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -152,9 +152,10 @@ static void macvlan_broadcast(struct sk_buff *skb,
 }
 
 /* called under rcu_read_lock() from netif_receive_skb */
-static struct sk_buff *macvlan_handle_frame(struct sk_buff *skb)
+static rx_handler_result_t macvlan_handle_frame(struct sk_buff **pskb)
 {
        struct macvlan_port *port;
+       struct sk_buff *skb = *pskb;
        const struct ethhdr *eth = eth_hdr(skb);
        const struct macvlan_dev *vlan;
        const struct macvlan_dev *src;
@@ -184,7 +185,7 @@ static struct sk_buff *macvlan_handle_frame(struct sk_buff *skb)
                         */
                        macvlan_broadcast(skb, port, src->dev,
                                          MACVLAN_MODE_VEPA);
-               return skb;
+               return RX_HANDLER_PASS;
        }
 
        if (port->passthru)
@@ -192,12 +193,12 @@ static struct sk_buff *macvlan_handle_frame(struct sk_buff *skb)
        else
                vlan = macvlan_hash_lookup(port, eth->h_dest);
        if (vlan == NULL)
-               return skb;
+               return RX_HANDLER_PASS;
 
        dev = vlan->dev;
        if (unlikely(!(dev->flags & IFF_UP))) {
                kfree_skb(skb);
-               return NULL;
+               return RX_HANDLER_CONSUMED;
        }
        len = skb->len + ETH_HLEN;
        skb = skb_share_check(skb, GFP_ATOMIC);
@@ -211,7 +212,7 @@ static struct sk_buff *macvlan_handle_frame(struct sk_buff *skb)
 
 out:
        macvlan_count_rx(vlan, len, ret == NET_RX_SUCCESS, 0);
-       return NULL;
+       return RX_HANDLER_CONSUMED;
 }
 
 static int macvlan_queue_xmit(struct sk_buff *skb, struct net_device *dev)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 604dbf5..5eeb2cd 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -390,7 +390,55 @@ enum gro_result {
 };
 typedef enum gro_result gro_result_t;
 
-typedef struct sk_buff *rx_handler_func_t(struct sk_buff *skb);
+/*
+ * enum rx_handler_result - Possible return values for rx_handlers.
+ * @RX_HANDLER_CONSUMED: skb was consumed by rx_handler, do not process it
+ * further.
+ * @RX_HANDLER_ANOTHER: Do another round in receive path. This is indicated in
+ * case skb->dev was changed by rx_handler.
+ * @RX_HANDLER_EXACT: Force exact delivery, no wildcard.
+ * @RX_HANDLER_PASS: Do nothing, passe the skb as if no rx_handler was called.
+ *
+ * rx_handlers are functions called from inside __netif_receive_skb(), to do
+ * special processing of the skb, prior to delivery to protocol handlers.
+ *
+ * Currently, a net_device can only have a single rx_handler registered. Trying
+ * to register a second rx_handler will return -EBUSY.
+ *
+ * To register a rx_handler on a net_device, use netdev_rx_handler_register().
+ * To unregister a rx_handler on a net_device, use
+ * netdev_rx_handler_unregister().
+ *
+ * Upon return, rx_handler is expected to tell __netif_receive_skb() what to
+ * do with the skb.
+ *
+ * If the rx_handler consumed to skb in some way, it should return
+ * RX_HANDLER_CONSUMED. This is appropriate when the rx_handler arranged for
+ * the skb to be delivered in some other ways.
+ *
+ * If the rx_handler changed skb->dev, to divert the skb to another
+ * net_device, it should return RX_HANDLER_ANOTHER. The rx_handler for the
+ * new device will be called if it exists.
+ *
+ * If the rx_handler consider the skb should be ignored, it should return
+ * RX_HANDLER_EXACT. The skb will only be delivered to protocol handlers that
+ * are registred on exact device (ptype->dev == skb->dev).
+ *
+ * If the rx_handler didn't changed skb->dev, but want the skb to be normally
+ * delivered, it should return RX_HANDLER_PASS.
+ *
+ * A device without a registered rx_handler will behave as if rx_handler
+ * returned RX_HANDLER_PASS.
+ */
+
+enum rx_handler_result {
+       RX_HANDLER_CONSUMED,
+       RX_HANDLER_ANOTHER,
+       RX_HANDLER_EXACT,
+       RX_HANDLER_PASS,
+};
+typedef enum rx_handler_result rx_handler_result_t;
+typedef rx_handler_result_t rx_handler_func_t(struct sk_buff **pskb);
 
 extern void __napi_schedule(struct napi_struct *n);
 

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 31f02d0..24cfa62 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -388,10 +388,7 @@ struct sk_buff {
        kmemcheck_bitfield_begin(flags2);
        __u16                   queue_mapping:16;
 #ifdef CONFIG_IPV6_NDISC_NODETYPE
-       __u8                    ndisc_nodetype:2,
-                               deliver_no_wcard:1;
-#else
-       __u8                    deliver_no_wcard:1;
+       __u8                    ndisc_nodetype:2;
 #endif
        __u8                    ooo_okay:1;
        kmemcheck_bitfield_end(flags2);

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 88e4aa9..e216079 100644 (file)
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -139,21 +139,22 @@ static inline int is_link_local(const unsigned char *dest)
  * Return NULL if skb is handled
  * note: already called with rcu_read_lock
  */
-struct sk_buff *br_handle_frame(struct sk_buff *skb)
+rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
 {
        struct net_bridge_port *p;
+       struct sk_buff *skb = *pskb;
        const unsigned char *dest = eth_hdr(skb)->h_dest;
        br_should_route_hook_t *rhook;
 
        if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
-               return skb;
+               return RX_HANDLER_PASS;
 
        if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
                goto drop;
 
        skb = skb_share_check(skb, GFP_ATOMIC);
        if (!skb)
-               return NULL;
+               return RX_HANDLER_CONSUMED;
 
        p = br_port_get_rcu(skb->dev);
 
@@ -167,10 +168,12 @@ struct sk_buff *br_handle_frame(struct sk_buff *skb)
                        goto forward;
 
                if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
-                           NULL, br_handle_local_finish))
-                       return NULL;    /* frame consumed by filter */
-               else
-                       return skb;     /* continue processing */
+                           NULL, br_handle_local_finish)) {
+                       return RX_HANDLER_CONSUMED; /* consumed by filter */
+               } else {
+                       *pskb = skb;
+                       return RX_HANDLER_PASS; /* continue processing */
+               }
        }
 
 forward:
@@ -178,8 +181,10 @@ forward:
        case BR_STATE_FORWARDING:
                rhook = rcu_dereference(br_should_route_hook);
                if (rhook) {
-                       if ((*rhook)(skb))
-                               return skb;
+                       if ((*rhook)(skb)) {
+                               *pskb = skb;
+                               return RX_HANDLER_PASS;
+                       }
                        dest = eth_hdr(skb)->h_dest;
                }
                /* fall through */
@@ -194,5 +199,5 @@ forward:
 drop:
                kfree_skb(skb);
        }
-       return NULL;
+       return RX_HANDLER_CONSUMED;
 }

diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index f7afc36..19e2f46 100644 (file)
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -379,7 +379,7 @@ extern void br_features_recompute(struct net_bridge *br);
 
 /* br_input.c */
 extern int br_handle_frame_finish(struct sk_buff *skb);
-extern struct sk_buff *br_handle_frame(struct sk_buff *skb);
+extern rx_handler_result_t br_handle_frame(struct sk_buff **pskb);
 
 /* br_ioctl.c */
 extern int br_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);

diff --git a/net/core/dev.c b/net/core/dev.c
index 0d39032..0b88eba 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3070,6 +3070,8 @@ out:
  *     on a failure.
  *
  *     The caller must hold the rtnl_mutex.
+ *
+ *     For a general description of rx_handler, see enum rx_handler_result.
  */
 int netdev_rx_handler_register(struct net_device *dev,
                               rx_handler_func_t *rx_handler,
@@ -3129,6 +3131,7 @@ static int __netif_receive_skb(struct sk_buff *skb)
        rx_handler_func_t *rx_handler;
        struct net_device *orig_dev;
        struct net_device *null_or_dev;
+       bool deliver_exact = false;
        int ret = NET_RX_DROP;
        __be16 type;
 
@@ -3181,18 +3184,22 @@ ncls:
 
        rx_handler = rcu_dereference(skb->dev->rx_handler);
        if (rx_handler) {
-               struct net_device *prev_dev;
-
                if (pt_prev) {
                        ret = deliver_skb(skb, pt_prev, orig_dev);
                        pt_prev = NULL;
                }
-               prev_dev = skb->dev;
-               skb = rx_handler(skb);
-               if (!skb)
+               switch (rx_handler(&skb)) {
+               case RX_HANDLER_CONSUMED:
                        goto out;
-               if (skb->dev != prev_dev)
+               case RX_HANDLER_ANOTHER:
                        goto another_round;
+               case RX_HANDLER_EXACT:
+                       deliver_exact = true;
+               case RX_HANDLER_PASS:
+                       break;
+               default:
+                       BUG();
+               }
        }
 
        if (vlan_tx_tag_present(skb)) {
@@ -3210,7 +3217,7 @@ ncls:
        vlan_on_bond_hook(skb);
 
        /* deliver only exact match when indicated */
-       null_or_dev = skb->deliver_no_wcard ? skb->dev : NULL;
+       null_or_dev = deliver_exact ? skb->dev : NULL;
 
        type = skb->protocol;
        list_for_each_entry_rcu(ptype,

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 1eb526a..801dd08 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -523,7 +523,6 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
        new->ip_summed          = old->ip_summed;
        skb_copy_queue_mapping(new, old);
        new->priority           = old->priority;
-       new->deliver_no_wcard   = old->deliver_no_wcard;
 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
        new->ipvs_property      = old->ipvs_property;
 #endif