1 /* 2 * net/dsa/tag_trailer.c - Trailer tag format handling 3 * Copyright (c) 2008-2009 Marvell Semiconductor 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 */ 10 11 #include <linux/etherdevice.h> 12 #include <linux/list.h> 13 #include <linux/slab.h> 14 15 #include "dsa_priv.h" 16 17 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev) 18 { 19 struct dsa_port *dp = dsa_slave_to_port(dev); 20 struct sk_buff *nskb; 21 int padlen; 22 u8 *trailer; 23 24 /* 25 * We have to make sure that the trailer ends up as the very 26 * last 4 bytes of the packet. This means that we have to pad 27 * the packet to the minimum ethernet frame size, if necessary, 28 * before adding the trailer. 29 */ 30 padlen = 0; 31 if (skb->len < 60) 32 padlen = 60 - skb->len; 33 34 nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC); 35 if (!nskb) 36 return NULL; 37 skb_reserve(nskb, NET_IP_ALIGN); 38 39 skb_reset_mac_header(nskb); 40 skb_set_network_header(nskb, skb_network_header(skb) - skb->head); 41 skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head); 42 skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len)); 43 consume_skb(skb); 44 45 if (padlen) { 46 skb_put_zero(nskb, padlen); 47 } 48 49 trailer = skb_put(nskb, 4); 50 trailer[0] = 0x80; 51 trailer[1] = 1 << dp->index; 52 trailer[2] = 0x10; 53 trailer[3] = 0x00; 54 55 return nskb; 56 } 57 58 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev, 59 struct packet_type *pt) 60 { 61 u8 *trailer; 62 int source_port; 63 64 if (skb_linearize(skb)) 65 return NULL; 66 67 trailer = skb_tail_pointer(skb) - 4; 68 if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 || 69 (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00) 70 return NULL; 71 72 source_port = trailer[1] & 7; 73 74 skb->dev = dsa_master_find_slave(dev, 0, source_port); 75 if (!skb->dev) 76 return NULL; 77 78 pskb_trim_rcsum(skb, skb->len - 4); 79 80 return skb; 81 } 82 83 const struct dsa_device_ops trailer_netdev_ops = { 84 .xmit = trailer_xmit, 85 .rcv = trailer_rcv, 86 }; 87