net/dsa/tag_hellcreek.c

   1 // SPDX-License-Identifier: (GPL-2.0 OR MIT)
   2 /*
   3  * net/dsa/tag_hellcreek.c - Hirschmann Hellcreek switch tag format handling
   4  *
   5  * Copyright (C) 2019,2020 Linutronix GmbH
   6  * Author Kurt Kanzenbach <kurt@linutronix.de>
   7  *
   8  * Based on tag_ksz.c.
   9  */
  10
  11 #include <linux/skbuff.h>
  12 #include <net/dsa.h>
  13
  14 #include "dsa_priv.h"
  15
  16 #define HELLCREEK_TAG_LEN       1
  17
  18 static struct sk_buff *hellcreek_xmit(struct sk_buff *skb,
  19                                       struct net_device *dev)
  20 {
  21         struct dsa_port *dp = dsa_slave_to_port(dev);
  22         u8 *tag;
  23
  24         /* Calculate checksums (if required) before adding the trailer tag to
  25          * avoid including it in calculations. That would lead to wrong
  26          * checksums after the switch strips the tag.
  27          */
  28         if (skb->ip_summed == CHECKSUM_PARTIAL &&
  29             skb_checksum_help(skb))
  30                 return NULL;
  31
  32         /* Tag encoding */
  33         tag  = skb_put(skb, HELLCREEK_TAG_LEN);
  34         *tag = BIT(dp->index);
  35
  36         return skb;
  37 }
  38
  39 static struct sk_buff *hellcreek_rcv(struct sk_buff *skb,
  40                                      struct net_device *dev)
  41 {
  42         /* Tag decoding */
  43         u8 *tag = skb_tail_pointer(skb) - HELLCREEK_TAG_LEN;
  44         unsigned int port = tag[0] & 0x03;
  45
  46         skb->dev = dsa_master_find_slave(dev, 0, port);
  47         if (!skb->dev) {
  48                 netdev_warn(dev, "Failed to get source port: %d\n", port);
  49                 return NULL;
  50         }
  51
  52         pskb_trim_rcsum(skb, skb->len - HELLCREEK_TAG_LEN);
  53
  54         dsa_default_offload_fwd_mark(skb);
  55
  56         return skb;
  57 }
  58
  59 static const struct dsa_device_ops hellcreek_netdev_ops = {
  60         .name     = "hellcreek",
  61         .proto    = DSA_TAG_PROTO_HELLCREEK,
  62         .xmit     = hellcreek_xmit,
  63         .rcv      = hellcreek_rcv,
  64         .needed_tailroom = HELLCREEK_TAG_LEN,
  65 };
  66
  67 MODULE_LICENSE("Dual MIT/GPL");
  68 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_HELLCREEK);
  69
  70 module_dsa_tag_driver(hellcreek_netdev_ops);