net/dsa/tag_trailer.c

0001 // SPDX-License-Identifier: GPL-2.0+
0002 /*
0003  * net/dsa/tag_trailer.c - Trailer tag format handling
0004  * Copyright (c) 2008-2009 Marvell Semiconductor
0005  */
0006
0007 #include <linux/etherdevice.h>
0008 #include <linux/list.h>
0009 #include <linux/slab.h>
0010
0011 #include "dsa_priv.h"
0012
0013 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
0014 {
0015     struct dsa_port *dp = dsa_slave_to_port(dev);
0016     u8 *trailer;
0017
0018     trailer = skb_put(skb, 4);
0019     trailer[0] = 0x80;
0020     trailer[1] = 1 << dp->index;
0021     trailer[2] = 0x10;
0022     trailer[3] = 0x00;
0023
0024     return skb;
0025 }
0026
0027 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev)
0028 {
0029     u8 *trailer;
0030     int source_port;
0031
0032     if (skb_linearize(skb))
0033         return NULL;
0034
0035     trailer = skb_tail_pointer(skb) - 4;
0036     if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
0037         (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
0038         return NULL;
0039
0040     source_port = trailer[1] & 7;
0041
0042     skb->dev = dsa_master_find_slave(dev, 0, source_port);
0043     if (!skb->dev)
0044         return NULL;
0045
0046     if (pskb_trim_rcsum(skb, skb->len - 4))
0047         return NULL;
0048
0049     return skb;
0050 }
0051
0052 static const struct dsa_device_ops trailer_netdev_ops = {
0053     .name   = "trailer",
0054     .proto  = DSA_TAG_PROTO_TRAILER,
0055     .xmit   = trailer_xmit,
0056     .rcv    = trailer_rcv,
0057     .needed_tailroom = 4,
0058 };
0059
0060 MODULE_LICENSE("GPL");
0061 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER);
0062
0063 module_dsa_tag_driver(trailer_netdev_ops);