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 "tag.h" 12 13 #define TRAILER_NAME "trailer" 14 15 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev) 16 { 17 struct dsa_port *dp = dsa_slave_to_port(dev); 18 u8 *trailer; 19 20 trailer = skb_put(skb, 4); 21 trailer[0] = 0x80; 22 trailer[1] = 1 << dp->index; 23 trailer[2] = 0x10; 24 trailer[3] = 0x00; 25 26 return skb; 27 } 28 29 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev) 30 { 31 u8 *trailer; 32 int source_port; 33 34 if (skb_linearize(skb)) 35 return NULL; 36 37 trailer = skb_tail_pointer(skb) - 4; 38 if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 || 39 (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00) 40 return NULL; 41 42 source_port = trailer[1] & 7; 43 44 skb->dev = dsa_master_find_slave(dev, 0, source_port); 45 if (!skb->dev) 46 return NULL; 47 48 if (pskb_trim_rcsum(skb, skb->len - 4)) 49 return NULL; 50 51 return skb; 52 } 53 54 static const struct dsa_device_ops trailer_netdev_ops = { 55 .name = TRAILER_NAME, 56 .proto = DSA_TAG_PROTO_TRAILER, 57 .xmit = trailer_xmit, 58 .rcv = trailer_rcv, 59 .needed_tailroom = 4, 60 }; 61 62 MODULE_LICENSE("GPL"); 63 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER, TRAILER_NAME); 64 65 module_dsa_tag_driver(trailer_netdev_ops); 66