packet: Add pre-defragmentation support for ipv4 fanouts.

The skb->rxhash cannot be properly computed if the
packet is a fragment.  To alleviate this, allow the
AF_PACKET client to ask for defragmentation to be
done at demux time.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 48 insertions, 2 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 3350f1d3c9aa..7ba6871a1942 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -223,7 +223,7 @@ struct packet_fanout {
         unsigned int            num_members;
         u16                     id;
         u8                      type;
-        u8                      pad;
+        u8                      defrag;
         atomic_t                rr_cur;
         struct list_head        list;
         struct sock             *arr[PACKET_FANOUT_MAX];
@@ -447,6 +447,41 @@ static struct sock *fanout_demux_lb(struct packet_fanout *f, struct sk_buff *skb
         return f->arr[cur];
 }
 
+static struct sk_buff *fanout_check_defrag(struct sk_buff *skb)
+{
+        const struct iphdr *iph;
+        u32 len;
+
+        if (skb->protocol != htons(ETH_P_IP))
+                return skb;
+
+        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+                return skb;
+
+        iph = ip_hdr(skb);
+        if (iph->ihl < 5 || iph->version != 4)
+                return skb;
+        if (!pskb_may_pull(skb, iph->ihl*4))
+                return skb;
+        iph = ip_hdr(skb);
+        len = ntohs(iph->tot_len);
+        if (skb->len < len || len < (iph->ihl * 4))
+                return skb;
+
+        if (ip_is_fragment(ip_hdr(skb))) {
+                skb = skb_clone(skb, GFP_ATOMIC);
+                if (skb) {
+                        if (pskb_trim_rcsum(skb, len))
+                                return skb;
+                        memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
+                        if (ip_defrag(skb, IP_DEFRAG_AF_PACKET))
+                                return NULL;
+                        skb->rxhash = 0;
+                }
+        }
+        return skb;
+}
+
 static int packet_rcv_fanout_hash(struct sk_buff *skb, struct net_device *dev,
                                   struct packet_type *pt, struct net_device *orig_dev)
 {
@@ -461,6 +496,12 @@ static int packet_rcv_fanout_hash(struct sk_buff *skb, struct net_device *dev,
                 return 0;
         }
 
+        if (f->defrag) {
+                skb = fanout_check_defrag(skb);
+                if (!skb)
+                        return 0;
+        }
+
         skb_get_rxhash(skb);
 
         sk = fanout_demux_hash(f, skb, num);
@@ -519,10 +560,12 @@ static void __fanout_unlink(struct sock *sk, struct packet_sock *po)
         spin_unlock(&f->lock);
 }
 
-static int fanout_add(struct sock *sk, u16 id, u8 type)
+static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
 {
         struct packet_sock *po = pkt_sk(sk);
         struct packet_fanout *f, *match;
+        u8 type = type_flags & 0xff;
+        u8 defrag = (type_flags & PACKET_FANOUT_FLAG_DEFRAG) ? 1 : 0;
         int err;
 
         switch (type) {
@@ -548,12 +591,15 @@ static int fanout_add(struct sock *sk, u16 id, u8 type)
                         break;
                 }
         }
+        if (match && match->defrag != defrag)
+                return -EINVAL;
         if (!match) {
                 match = kzalloc(sizeof(*match), GFP_KERNEL);
                 if (match) {
                         write_pnet(&match->net, sock_net(sk));
                         match->id = id;
                         match->type = type;
+                        match->defrag = defrag;
                         atomic_set(&match->rr_cur, 0);
                         INIT_LIST_HEAD(&match->list);
                         spin_lock_init(&match->lock);