1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * net/dsa/tag_trailer.c - Trailer tag format handling 4 * Copyright (c) 2008-2009 Marvell Semiconductor 5 */ 6 7 #include <linux/etherdevice.h> 8 #include <linux/list.h> 9 #include <linux/slab.h> 10 11 #include "dsa_priv.h" 12 13 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev) 14 { 15 struct dsa_port *dp = dsa_slave_to_port(dev); 16 u8 *trailer; 17 18 trailer = skb_put(skb, 4); 19 trailer[0] = 0x80; 20 trailer[1] = 1 << dp->index; 21 trailer[2] = 0x10; 22 trailer[3] = 0x00; 23 24 return skb; 25 } 26 27 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev, 28 struct packet_type *pt) 29 { 30 u8 *trailer; 31 int source_port; 32 33 if (skb_linearize(skb)) 34 return NULL; 35 36 trailer = skb_tail_pointer(skb) - 4; 37 if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 || 38 (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00) 39 return NULL; 40 41 source_port = trailer[1] & 7; 42 43 skb->dev = dsa_master_find_slave(dev, 0, source_port); 44 if (!skb->dev) 45 return NULL; 46 47 if (pskb_trim_rcsum(skb, skb->len - 4)) 48 return NULL; 49 50 return skb; 51 } 52 53 static const struct dsa_device_ops trailer_netdev_ops = { 54 .name = "trailer", 55 .proto = DSA_TAG_PROTO_TRAILER, 56 .xmit = trailer_xmit, 57 .rcv = trailer_rcv, 58 .overhead = 4, 59 .tail_tag = true, 60 }; 61 62 MODULE_LICENSE("GPL"); 63 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER); 64 65 module_dsa_tag_driver(trailer_netdev_ops); 66