Staging: batman-adv: Create copy of skb with pre-allocated headroom

We can use skb_cow instead of a handwritten function to test and create
a writable skb buffer. This also allows us to pre-allocate headroom to
be able to send the data without re-allocating the buffer again to add
the ethernet header.

Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/batman-adv/routing.c b/drivers/staging/batman-adv/routing.c
index d8e77ac..7e993a2 100644 (file)
--- a/drivers/staging/batman-adv/routing.c
+++ b/drivers/staging/batman-adv/routing.c
@@ -742,7 +742,6 @@ int recv_bat_packet(struct sk_buff *skb,
 {
        struct ethhdr *ethhdr;
        unsigned long flags;
-       struct sk_buff *skb_old;
 
        /* drop packet if it has not necessary minimum size */
        if (skb_headlen(skb) < sizeof(struct batman_packet))
@@ -758,18 +757,11 @@ int recv_bat_packet(struct sk_buff *skb,
        if (is_bcast(ethhdr->h_source))
                return NET_RX_DROP;
 
-       /* TODO: we use headlen instead of "length", because
-        * only this data is paged in. */
-
        /* create a copy of the skb, if needed, to modify it. */
-       if (!skb_clone_writable(skb, skb_headlen(skb))) {
-               skb_old = skb;
-               skb = skb_copy(skb, GFP_ATOMIC);
-               if (!skb)
-                       return NET_RX_DROP;
-               ethhdr = (struct ethhdr *)skb_mac_header(skb);
-               kfree_skb(skb_old);
-       }
+       if (skb_cow(skb, 0) < 0)
+               return NET_RX_DROP;
+
+       ethhdr = (struct ethhdr *)skb_mac_header(skb);
 
        spin_lock_irqsave(&orig_hash_lock, flags);
        receive_aggr_bat_packet(ethhdr,
@@ -789,7 +781,6 @@ static int recv_my_icmp_packet(struct sk_buff *skb, size_t icmp_len)
        struct orig_node *orig_node;
        struct icmp_packet_rr *icmp_packet;
        struct ethhdr *ethhdr;
-       struct sk_buff *skb_old;
        struct batman_if *batman_if;
        int ret;
        unsigned long flags;
@@ -824,16 +815,11 @@ static int recv_my_icmp_packet(struct sk_buff *skb, size_t icmp_len)
                spin_unlock_irqrestore(&orig_hash_lock, flags);
 
                /* create a copy of the skb, if needed, to modify it. */
-               skb_old = NULL;
-               if (!skb_clone_writable(skb, icmp_len)) {
-                       skb_old = skb;
-                       skb = skb_copy(skb, GFP_ATOMIC);
-                       if (!skb)
-                               return NET_RX_DROP;
-                       icmp_packet = (struct icmp_packet_rr *)skb->data;
-                       ethhdr = (struct ethhdr *)skb_mac_header(skb);
-                       kfree_skb(skb_old);
-               }
+               if (skb_cow(skb, sizeof(struct ethhdr)) < 0)
+                       return NET_RX_DROP;
+
+               icmp_packet = (struct icmp_packet_rr *)skb->data;
+               ethhdr = (struct ethhdr *)skb_mac_header(skb);
 
                memcpy(icmp_packet->dst, icmp_packet->orig, ETH_ALEN);
                memcpy(icmp_packet->orig,
@@ -857,7 +843,6 @@ static int recv_icmp_ttl_exceeded(struct sk_buff *skb, size_t icmp_len)
        struct orig_node *orig_node;
        struct icmp_packet *icmp_packet;
        struct ethhdr *ethhdr;
-       struct sk_buff *skb_old;
        struct batman_if *batman_if;
        int ret;
        unsigned long flags;
@@ -893,15 +878,11 @@ static int recv_icmp_ttl_exceeded(struct sk_buff *skb, size_t icmp_len)
                spin_unlock_irqrestore(&orig_hash_lock, flags);
 
                /* create a copy of the skb, if needed, to modify it. */
-               if (!skb_clone_writable(skb, icmp_len)) {
-                       skb_old = skb;
-                       skb = skb_copy(skb, GFP_ATOMIC);
-                       if (!skb)
-                               return NET_RX_DROP;
-                       icmp_packet = (struct icmp_packet *) skb->data;
-                       ethhdr = (struct ethhdr *)skb_mac_header(skb);
-                       kfree_skb(skb_old);
-               }
+               if (skb_cow(skb, sizeof(struct ethhdr)) < 0)
+                       return NET_RX_DROP;
+
+               icmp_packet = (struct icmp_packet *) skb->data;
+               ethhdr = (struct ethhdr *)skb_mac_header(skb);
 
                memcpy(icmp_packet->dst, icmp_packet->orig, ETH_ALEN);
                memcpy(icmp_packet->orig,
@@ -924,7 +905,6 @@ int recv_icmp_packet(struct sk_buff *skb)
        struct icmp_packet_rr *icmp_packet;
        struct ethhdr *ethhdr;
        struct orig_node *orig_node;
-       struct sk_buff *skb_old;
        struct batman_if *batman_if;
        int hdr_size = sizeof(struct icmp_packet);
        int ret;
@@ -990,15 +970,11 @@ int recv_icmp_packet(struct sk_buff *skb)
                spin_unlock_irqrestore(&orig_hash_lock, flags);
 
                /* create a copy of the skb, if needed, to modify it. */
-               if (!skb_clone_writable(skb, hdr_size)) {
-                       skb_old = skb;
-                       skb = skb_copy(skb, GFP_ATOMIC);
-                       if (!skb)
-                               return NET_RX_DROP;
-                       icmp_packet = (struct icmp_packet_rr *)skb->data;
-                       ethhdr = (struct ethhdr *)skb_mac_header(skb);
-                       kfree_skb(skb_old);
-               }
+               if (skb_cow(skb, sizeof(struct ethhdr)) < 0)
+                       return NET_RX_DROP;
+
+               icmp_packet = (struct icmp_packet_rr *)skb->data;
+               ethhdr = (struct ethhdr *)skb_mac_header(skb);
 
                /* decrement ttl */
                icmp_packet->ttl--;
@@ -1137,7 +1113,6 @@ static int route_unicast_packet(struct sk_buff *skb, struct batman_if *recv_if,
        struct orig_node *orig_node;
        struct neigh_node *router;
        struct batman_if *batman_if;
-       struct sk_buff *skb_old;
        uint8_t dstaddr[ETH_ALEN];
        unsigned long flags;
        struct unicast_packet *unicast_packet =
@@ -1173,15 +1148,11 @@ static int route_unicast_packet(struct sk_buff *skb, struct batman_if *recv_if,
        spin_unlock_irqrestore(&orig_hash_lock, flags);
 
        /* create a copy of the skb, if needed, to modify it. */
-       if (!skb_clone_writable(skb, hdr_size)) {
-               skb_old = skb;
-               skb = skb_copy(skb, GFP_ATOMIC);
-               if (!skb)
-                       return NET_RX_DROP;
-               unicast_packet = (struct unicast_packet *) skb->data;
-               ethhdr = (struct ethhdr *)skb_mac_header(skb);
-               kfree_skb(skb_old);
-       }
+       if (skb_cow(skb, sizeof(struct ethhdr)) < 0)
+               return NET_RX_DROP;
+
+       unicast_packet = (struct unicast_packet *) skb->data;
+       ethhdr = (struct ethhdr *)skb_mac_header(skb);
 
        /* decrement ttl */
        unicast_packet->ttl--;