1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * net/dsa/tag_dsa.c - (Non-ethertype) DSA tagging 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 #define DSA_HLEN 4 14 15 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev) 16 { 17 struct dsa_port *dp = dsa_slave_to_port(dev); 18 u8 *dsa_header; 19 20 /* 21 * Convert the outermost 802.1q tag to a DSA tag for tagged 22 * packets, or insert a DSA tag between the addresses and 23 * the ethertype field for untagged packets. 24 */ 25 if (skb->protocol == htons(ETH_P_8021Q)) { 26 if (skb_cow_head(skb, 0) < 0) 27 return NULL; 28 29 /* 30 * Construct tagged FROM_CPU DSA tag from 802.1q tag. 31 */ 32 dsa_header = skb->data + 2 * ETH_ALEN; 33 dsa_header[0] = 0x60 | dp->ds->index; 34 dsa_header[1] = dp->index << 3; 35 36 /* 37 * Move CFI field from byte 2 to byte 1. 38 */ 39 if (dsa_header[2] & 0x10) { 40 dsa_header[1] |= 0x01; 41 dsa_header[2] &= ~0x10; 42 } 43 } else { 44 if (skb_cow_head(skb, DSA_HLEN) < 0) 45 return NULL; 46 skb_push(skb, DSA_HLEN); 47 48 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN); 49 50 /* 51 * Construct untagged FROM_CPU DSA tag. 52 */ 53 dsa_header = skb->data + 2 * ETH_ALEN; 54 dsa_header[0] = 0x40 | dp->ds->index; 55 dsa_header[1] = dp->index << 3; 56 dsa_header[2] = 0x00; 57 dsa_header[3] = 0x00; 58 } 59 60 return skb; 61 } 62 63 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev, 64 struct packet_type *pt) 65 { 66 u8 *dsa_header; 67 int source_device; 68 int source_port; 69 70 if (unlikely(!pskb_may_pull(skb, DSA_HLEN))) 71 return NULL; 72 73 /* 74 * The ethertype field is part of the DSA header. 75 */ 76 dsa_header = skb->data - 2; 77 78 /* 79 * Check that frame type is either TO_CPU or FORWARD. 80 */ 81 if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0) 82 return NULL; 83 84 /* 85 * Determine source device and port. 86 */ 87 source_device = dsa_header[0] & 0x1f; 88 source_port = (dsa_header[1] >> 3) & 0x1f; 89 90 skb->dev = dsa_master_find_slave(dev, source_device, source_port); 91 if (!skb->dev) 92 return NULL; 93 94 /* 95 * Convert the DSA header to an 802.1q header if the 'tagged' 96 * bit in the DSA header is set. If the 'tagged' bit is clear, 97 * delete the DSA header entirely. 98 */ 99 if (dsa_header[0] & 0x20) { 100 u8 new_header[4]; 101 102 /* 103 * Insert 802.1q ethertype and copy the VLAN-related 104 * fields, but clear the bit that will hold CFI (since 105 * DSA uses that bit location for another purpose). 106 */ 107 new_header[0] = (ETH_P_8021Q >> 8) & 0xff; 108 new_header[1] = ETH_P_8021Q & 0xff; 109 new_header[2] = dsa_header[2] & ~0x10; 110 new_header[3] = dsa_header[3]; 111 112 /* 113 * Move CFI bit from its place in the DSA header to 114 * its 802.1q-designated place. 115 */ 116 if (dsa_header[1] & 0x01) 117 new_header[2] |= 0x10; 118 119 /* 120 * Update packet checksum if skb is CHECKSUM_COMPLETE. 121 */ 122 if (skb->ip_summed == CHECKSUM_COMPLETE) { 123 __wsum c = skb->csum; 124 c = csum_add(c, csum_partial(new_header + 2, 2, 0)); 125 c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0)); 126 skb->csum = c; 127 } 128 129 memcpy(dsa_header, new_header, DSA_HLEN); 130 } else { 131 /* 132 * Remove DSA tag and update checksum. 133 */ 134 skb_pull_rcsum(skb, DSA_HLEN); 135 memmove(skb->data - ETH_HLEN, 136 skb->data - ETH_HLEN - DSA_HLEN, 137 2 * ETH_ALEN); 138 } 139 140 skb->offload_fwd_mark = 1; 141 142 return skb; 143 } 144 145 static int dsa_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto, 146 int *offset) 147 { 148 *offset = 4; 149 *proto = ((__be16 *)skb->data)[1]; 150 return 0; 151 } 152 153 static const struct dsa_device_ops dsa_netdev_ops = { 154 .name = "dsa", 155 .proto = DSA_TAG_PROTO_DSA, 156 .xmit = dsa_xmit, 157 .rcv = dsa_rcv, 158 .flow_dissect = dsa_tag_flow_dissect, 159 .overhead = DSA_HLEN, 160 }; 161 162 MODULE_LICENSE("GPL"); 163 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA); 164 165 module_dsa_tag_driver(dsa_netdev_ops); 166