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 struct sk_buff *nskb; 17 int padlen; 18 u8 *trailer; 19 20 /* 21 * We have to make sure that the trailer ends up as the very 22 * last 4 bytes of the packet. This means that we have to pad 23 * the packet to the minimum ethernet frame size, if necessary, 24 * before adding the trailer. 25 */ 26 padlen = 0; 27 if (skb->len < 60) 28 padlen = 60 - skb->len; 29 30 nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC); 31 if (!nskb) 32 return NULL; 33 skb_reserve(nskb, NET_IP_ALIGN); 34 35 skb_reset_mac_header(nskb); 36 skb_set_network_header(nskb, skb_network_header(skb) - skb->head); 37 skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head); 38 skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len)); 39 consume_skb(skb); 40 41 if (padlen) { 42 skb_put_zero(nskb, padlen); 43 } 44 45 trailer = skb_put(nskb, 4); 46 trailer[0] = 0x80; 47 trailer[1] = 1 << dp->index; 48 trailer[2] = 0x10; 49 trailer[3] = 0x00; 50 51 return nskb; 52 } 53 54 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev, 55 struct packet_type *pt) 56 { 57 u8 *trailer; 58 int source_port; 59 60 if (skb_linearize(skb)) 61 return NULL; 62 63 trailer = skb_tail_pointer(skb) - 4; 64 if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 || 65 (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00) 66 return NULL; 67 68 source_port = trailer[1] & 7; 69 70 skb->dev = dsa_master_find_slave(dev, 0, source_port); 71 if (!skb->dev) 72 return NULL; 73 74 if (pskb_trim_rcsum(skb, skb->len - 4)) 75 return NULL; 76 77 return skb; 78 } 79 80 static const struct dsa_device_ops trailer_netdev_ops = { 81 .name = "trailer", 82 .proto = DSA_TAG_PROTO_TRAILER, 83 .xmit = trailer_xmit, 84 .rcv = trailer_rcv, 85 .overhead = 4, 86 }; 87 88 MODULE_LICENSE("GPL"); 89 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER); 90 91 module_dsa_tag_driver(trailer_netdev_ops); 92