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 { 29 u8 *trailer; 30 int source_port; 31 32 if (skb_linearize(skb)) 33 return NULL; 34 35 trailer = skb_tail_pointer(skb) - 4; 36 if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 || 37 (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00) 38 return NULL; 39 40 source_port = trailer[1] & 7; 41 42 skb->dev = dsa_master_find_slave(dev, 0, source_port); 43 if (!skb->dev) 44 return NULL; 45 46 if (pskb_trim_rcsum(skb, skb->len - 4)) 47 return NULL; 48 49 return skb; 50 } 51 52 static const struct dsa_device_ops trailer_netdev_ops = { 53 .name = "trailer", 54 .proto = DSA_TAG_PROTO_TRAILER, 55 .xmit = trailer_xmit, 56 .rcv = trailer_rcv, 57 .needed_tailroom = 4, 58 }; 59 60 MODULE_LICENSE("GPL"); 61 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER); 62 63 module_dsa_tag_driver(trailer_netdev_ops); 64