diff options
Diffstat (limited to 'net/dsa/tag_rtl4_a.c')
| -rw-r--r-- | net/dsa/tag_rtl4_a.c | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/net/dsa/tag_rtl4_a.c b/net/dsa/tag_rtl4_a.c new file mode 100644 index 000000000000..7b63010fa87b --- /dev/null +++ b/net/dsa/tag_rtl4_a.c @@ -0,0 +1,130 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Handler for Realtek 4 byte DSA switch tags + * Currently only supports protocol "A" found in RTL8366RB + * Copyright (c) 2020 Linus Walleij <linus.walleij@linaro.org> + * + * This "proprietary tag" header looks like so: + * + * ------------------------------------------------- + * | MAC DA | MAC SA | 0x8899 | 2 bytes tag | Type | + * ------------------------------------------------- + * + * The 2 bytes tag form a 16 bit big endian word. The exact + * meaning has been guessed from packet dumps from ingress + * frames, as no working egress traffic has been available + * we do not know the format of the egress tags or if they + * are even supported. + */ + +#include <linux/etherdevice.h> +#include <linux/bits.h> + +#include "dsa_priv.h" + +#define RTL4_A_HDR_LEN 4 +#define RTL4_A_ETHERTYPE 0x8899 +#define RTL4_A_PROTOCOL_SHIFT 12 +/* + * 0x1 = Realtek Remote Control protocol (RRCP) + * 0x2/0x3 seems to be used for loopback testing + * 0x9 = RTL8306 DSA protocol + * 0xa = RTL8366RB DSA protocol + */ +#define RTL4_A_PROTOCOL_RTL8366RB 0xa + +static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb, + struct net_device *dev) +{ + /* + * Just let it pass thru, we don't know if it is possible + * to tag a frame with the 0x8899 ethertype and direct it + * to a specific port, all attempts at reverse-engineering have + * ended up with the frames getting dropped. + * + * The VLAN set-up needs to restrict the frames to the right port. + * + * If you have documentation on the tagging format for RTL8366RB + * (tag type A) then please contribute. + */ + return skb; +} + +static struct sk_buff *rtl4a_tag_rcv(struct sk_buff *skb, + struct net_device *dev, + struct packet_type *pt) +{ + u16 protport; + __be16 *p; + u16 etype; + u8 *tag; + u8 prot; + u8 port; + + if (unlikely(!pskb_may_pull(skb, RTL4_A_HDR_LEN))) + return NULL; + + /* The RTL4 header has its own custom Ethertype 0x8899 and that + * starts right at the beginning of the packet, after the src + * ethernet addr. Apparantly skb->data always points 2 bytes in, + * behind the Ethertype. + */ + tag = skb->data - 2; + p = (__be16 *)tag; + etype = ntohs(*p); + if (etype != RTL4_A_ETHERTYPE) { + /* Not custom, just pass through */ + netdev_dbg(dev, "non-realtek ethertype 0x%04x\n", etype); + return skb; + } + p = (__be16 *)(tag + 2); + protport = ntohs(*p); + /* The 4 upper bits are the protocol */ + prot = (protport >> RTL4_A_PROTOCOL_SHIFT) & 0x0f; + if (prot != RTL4_A_PROTOCOL_RTL8366RB) { + netdev_err(dev, "unknown realtek protocol 0x%01x\n", prot); + return NULL; + } + port = protport & 0xff; + + skb->dev = dsa_master_find_slave(dev, 0, port); + if (!skb->dev) { + netdev_dbg(dev, "could not find slave for port %d\n", port); + return NULL; + } + + /* Remove RTL4 tag and recalculate checksum */ + skb_pull_rcsum(skb, RTL4_A_HDR_LEN); + + /* Move ethernet DA and SA in front of the data */ + memmove(skb->data - ETH_HLEN, + skb->data - ETH_HLEN - RTL4_A_HDR_LEN, + 2 * ETH_ALEN); + + skb->offload_fwd_mark = 1; + + return skb; +} + +static int rtl4a_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto, + int *offset) +{ + *offset = RTL4_A_HDR_LEN; + /* Skip past the tag and fetch the encapsulated Ethertype */ + *proto = ((__be16 *)skb->data)[1]; + + return 0; +} + +static const struct dsa_device_ops rtl4a_netdev_ops = { + .name = "rtl4a", + .proto = DSA_TAG_PROTO_RTL4_A, + .xmit = rtl4a_tag_xmit, + .rcv = rtl4a_tag_rcv, + .flow_dissect = rtl4a_tag_flow_dissect, + .overhead = RTL4_A_HDR_LEN, +}; +module_dsa_tag_driver(rtl4a_netdev_ops); + +MODULE_LICENSE("GPL"); +MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL4_A); |