[LRO]: fix lro_gen_skb() alignment

Add a field to the lro_mgr struct so that drivers can specify how much
padding is required to align layer 3 headers when a packet is copied
into a freshly allocated skb by inet_lro.c:lro_gen_skb().  Without
padding, skbs generated by LRO will cause alignment warnings on
architectures which require strict alignment (seen on sparc64).

Myri10GE is updated to use this field.

Signed-off-by: Andrew Gallatin <gallatin@myri.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/myri10ge/myri10ge.c

@@ -1979,6 +1979,7 @@ static int myri10ge_open(struct net_device *dev)
 	lro_mgr->lro_arr = mgp->rx_done.lro_desc;
 	lro_mgr->get_frag_header = myri10ge_get_frag_header;
 	lro_mgr->max_aggr = myri10ge_lro_max_pkts;
+	lro_mgr->frag_align_pad = 2;
 	if (lro_mgr->max_aggr > MAX_SKB_FRAGS)
 		lro_mgr->max_aggr = MAX_SKB_FRAGS;
 

include/linux/inet_lro.h

@@ -91,6 +91,9 @@ struct net_lro_mgr {
 	int max_desc; /* Max number of LRO descriptors  */
 	int max_aggr; /* Max number of LRO packets to be aggregated */
 
+	int frag_align_pad; /* Padding required to properly align layer 3
+			     * headers in generated skb when using frags */
+
 	struct net_lro_desc *lro_arr; /* Array of LRO descriptors */
 
 	/*

net/ipv4/inet_lro.c

@@ -401,10 +401,11 @@ static struct sk_buff *lro_gen_skb(struct net_lro_mgr *lro_mgr,
 	int data_len = len;
 	int hdr_len = min(len, hlen);
 
-	skb = netdev_alloc_skb(lro_mgr->dev, hlen);
+	skb = netdev_alloc_skb(lro_mgr->dev, hlen + lro_mgr->frag_align_pad);
 	if (!skb)
 		return NULL;
 
+	skb_reserve(skb, lro_mgr->frag_align_pad);
 	skb->len = len;
 	skb->data_len = len - hdr_len;
 	skb->truesize += true_size;