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Feb 15, 2025
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Linux: handle other DSA tags. #1463

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284 changes: 280 additions & 4 deletions pcap-linux.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5404,23 +5404,299 @@ iface_get_offload(pcap_t *handle _U_)
}
#endif /* SIOCETHTOOL */

/*
* As per
*
* https://www.kernel.org/doc/html/latest/networking/dsa/dsa.html#switch-tagging-protocols
*
* Type 1 means that the tag is prepended to the Ethernet packet.
* LINKTYPE_ETHERNET/DLT_EN10MB doesn't work, as it would try to
* dissect the tag data as the Ethernet header. These should get
* their own LINKTYPE_DLT_ values.
*
* Type 2 means that the tag is inserted into the Ethernet header
* after the source address and before the type/length field.
*
* Type 3 means that tag is a packet trailer. LINKTYPE_ETHERNET/DLT_EN10MB
* works, unless the next-layer protocol has no length field of its own,
* so that the tag might be treated as part of the payload. These should
* get their own LINKTYPE_/DLT_ values.
*
* If you get an "unsupported DSA tag" error, please add the tag to here,
* complete with a full comment indicating whether it's type 1, 2, or 3,
* and, for type 2, indicating whether it has an Ethertype and, if so
* what that type is, and whether it's registered with the IEEE or is
* self-assigned. Also, point to *something* that indicates the format
* of the tag.
*/
static struct dsa_proto {
const char *name;
bpf_u_int32 linktype;
} dsa_protos[] = {
/*
* None is special and indicates that the interface does not have
* any tagging protocol configured, and is therefore a standard
* Ethernet interface.
* Type 1. See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_ar9331.c
*/
{ "ar9331", DLT_EN10MB },

/*
* Type 2, without an Ethertype at the beginning,
* assigned a LINKTYPE_/DLT_ value.
*/
{ "none", DLT_EN10MB },
{ "brcm", DLT_DSA_TAG_BRCM },

/*
* Type 2, with Ethertype 0x8874, assigned to Broadcom.
*
* This doies not require a LINKTYPE_/DLT_ value, it
* just requires that Ethertype 0x8874 be dissected
* properly.
*/
{ "brcm-legacy", DLT_EN10MB },

/*
* Type 1.
*/
{ "brcm-prepend", DLT_DSA_TAG_BRCM_PREPEND },

/*
* Type 2, without an Etherype at he beginning,
* assigned a LINKTYPE_/DLT_ value.
*/
{ "dsa", DLT_DSA_TAG_DSA },

/*
* Type 2, with an Ethertype field, but without
* an assigned Ethertype value that can be relied
* on; assigned a LINKTYPE_/DLT_ value.
*/
{ "edsa", DLT_DSA_TAG_EDSA },

/*
* Type 1, with different transmit and receive headers,
* so can't really be handled well with the current
* libpcap API and with pcap files. Use DLT_LINUX_SLL,
* to get the direction?
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_gswip.c
*/
{ "gswip", DLT_EN10MB },

/*
* Type 3. See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_hellcreek.c
*/
{ "hellcreek", DLT_EN10MB },

/*
* Type 3, with different transmit and receive headers,
* so can't really be handled well with the current
* libpcap API and with pcap files. Use DLT_LINUX_SLL,
* to get the direction?
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_ksz.c#L102
*/
{ "ksz8795", DLT_EN10MB },

/*
* Type 3, with different transmit and receive headers,
* so can't really be handled well with the current
* libpcap API and with pcap files. Use DLT_LINUX_SLL,
* to get the direction?
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_ksz.c#L160
*/
{ "ksz9477", DLT_EN10MB },

/*
* Type 3, with different transmit and receive headers,
* so can't really be handled well with the current
* libpcap API and with pcap files. Use DLT_LINUX_SLL,
* to get the direction?
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_ksz.c#L341
*/
{ "ksz9893", DLT_EN10MB },

/*
* Type 3, with different transmit and receive headers,
* so can't really be handled well with the current
* libpcap API and with pcap files. Use DLT_LINUX_SLL,
* to get the direction?
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_ksz.c#L386
*/
{ "lan937x", DLT_EN10MB },

/*
* Type 2, with Ethertype 0x8100; the VID can be interpreted
* as per
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_lan9303.c#L24
*
* so giving its own LINKTYPE_/DLT_ value would allow a
* dissector to do so.
*/
{ "lan9303", DLT_EN10MB },

/*
* Type 2, without an Etherype at he beginning,
* should be assigned a LINKTYPE_/DLT_ value.
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_mtk.c#L15
*/
{ "mtk", DLT_EN10MB },

/*
* None is special and indicates that the interface does not have
* any tagging protocol configured, and is therefore a standard
* Ethernet interface.
*/
{ "none", DLT_EN10MB },

/*
* Type 1.
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_ocelot.c
*/
{ "ocelot", DLT_EN10MB },

/*
* Type 1.
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_ocelot.c
*/
{ "seville", DLT_EN10MB },

/*
* Type 2, with Ethertype 0x8100; the VID can be interpreted
* as per
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_8021q.c#L15
*
* so giving its own LINKTYPE_/DLT_ value would allow a
* dissector to do so.
*/
{ "ocelot-8021q", DLT_EN10MB },

/*
* Type 2, without an Etherype at he beginning,
* should be assigned a LINKTYPE_/DLT_ value.
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_qca.c
*/
{ "qca", DLT_EN10MB },

/*
* Type 2, with Ethertype 0x8899, assigned to Realtek;
* they use it for several on-the-Ethernet protocols
* as well, but there are fields that allow the two
* tag formats, and all the protocols in question,
* to be distinguiished from one another.
*
* This doies not require a LINKTYPE_/DLT_ value, it
* just requires that Ethertype 0x8899 be dissected
* properly.
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_rtl4_a.c
*
* http://realtek.info/pdf/rtl8306sd%28m%29_datasheet_1.1.pdf
*
* and various pages in tcpdump's print-realtek.c and Wireshark's
* epan/dissectors/packet-realtek.c for the other protocols.
*/
{ "rtl4a", DLT_EN10MB },

/*
* Type 2, with Ethertype 0x8899, assigned to Realtek;
* see above.
*/
{ "rtl8_4", DLT_EN10MB },

/*
* Type 3, with the same tag format as rtl8_4.
*/
{ "rtl8_4t", DLT_EN10MB },

/*
* Type 2, with Ethertype 0xe001; that's probably
* self-assigned, so this really should ahve its
* own LINKTYPE_/DLT_ value.
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_rzn1_a5psw.c
*/
{ "a5psw", DLT_EN10MB },

/*
* Type 2, with Ethertype 0x8100 or the self-assigned
* 0xdadb, so this really should ahve its own
* LINKTYPE_/DLT_ value; that would also allow the
* VID of the tag to be dissected as per
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_8021q.c#L15
*/
{ "sja1105", DLT_EN10MB },

/*
* Type "none of the above", with both a header and trailer,
* with different transmit and receive tags. Has
* Ethertype 0xdadc, which is probably self-assigned.
* This should really have its own LINKTYPE_/DLT_ value.
*/
{ "sja1110", DLT_EN10MB },

/*
* Type 3, as the name suggests.
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_trailer.c
*/
{ "trailer", DLT_EN10MB },

/*
* Type 2, with Ethertype 0x8100; the VID can be interpreted
* as per
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_8021q.c#L15
*
* so giving its own LINKTYPE_/DLT_ value would allow a
* dissector to do so.
*/
{ "vsc73xx-8021q", DLT_EN10MB },

/*
* Type 3.
*
* See
*
* https://elixir.bootlin.com/linux/v6.13.2/source/net/dsa/tag_xrs700x.c
*/
{ "xrs700x", DLT_EN10MB },
};

static int
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