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flow_dissector: Add PPPoE dissectors 

Allow to dissect PPPoE specific fields which are:
- session ID (16 bits)
- ppp protocol (16 bits)
- type (16 bits) - this is PPPoE ethertype, for now only
  ETH_P_PPP_SES is supported, possible ETH_P_PPP_DISC
  in the future

The goal is to make the following TC command possible:

  # tc filter add dev ens6f0 ingress prio 1 protocol ppp_ses \
      flower \
        pppoe_sid 12 \
        ppp_proto ip \
      action drop

Note that only PPPoE Session is supported.

Signed-off-by: Wojciech Drewek <wojciech.drewek@intel.com>
Acked-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
This commit is contained in:
Wojciech Drewek 2022-07-18 14:18:10 +02:00 committed by Tony Nguyen
parent 35d099da41
commit 46126db9c8
3 changed files with 77 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/ppp_defs.h
View File

@ -11,4 +11,18 @@
#include <uapi/linux/ppp_defs.h>
#define PPP_FCS(fcs, c) crc_ccitt_byte(fcs, c)
/**
* ppp_proto_is_valid - checks if PPP protocol is valid
* @proto: PPP protocol
*
* Assumes proto is not compressed.
* Protocol is valid if the value is odd and the least significant bit of the
* most significant octet is 0 (see RFC 1661, section 2).
*/
static inline bool ppp_proto_is_valid(u16 proto)
{
return !!((proto & 0x0101) == 0x0001);
}
#endif /* _PPP_DEFS_H_ */

13
include/net/flow_dissector.h
View File

@ -277,6 +277,18 @@ struct flow_dissector_key_num_of_vlans {
u8 num_of_vlans;
};
/**
* struct flow_dissector_key_pppoe:
* @session_id: pppoe session id
* @ppp_proto: ppp protocol
* @type: pppoe eth type
*/
struct flow_dissector_key_pppoe {
__be16 session_id;
__be16 ppp_proto;
__be16 type;
};
enum flow_dissector_key_id {
FLOW_DISSECTOR_KEY_CONTROL, /* struct flow_dissector_key_control */
FLOW_DISSECTOR_KEY_BASIC, /* struct flow_dissector_key_basic */
@ -307,6 +319,7 @@ enum flow_dissector_key_id {
FLOW_DISSECTOR_KEY_CT, /* struct flow_dissector_key_ct */
FLOW_DISSECTOR_KEY_HASH, /* struct flow_dissector_key_hash */
FLOW_DISSECTOR_KEY_NUM_OF_VLANS, /* struct flow_dissector_key_num_of_vlans */
FLOW_DISSECTOR_KEY_PPPOE, /* struct flow_dissector_key_pppoe */
FLOW_DISSECTOR_KEY_MAX,
};

61
net/core/flow_dissector.c
View File

@ -895,6 +895,11 @@ bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
return result == BPF_OK;
}
static bool is_pppoe_ses_hdr_valid(struct pppoe_hdr hdr)
{
return hdr.ver == 1 && hdr.type == 1 && hdr.code == 0;
}
/**
* __skb_flow_dissect - extract the flow_keys struct and return it
* @net: associated network namespace, derived from @skb if NULL
@ -1214,26 +1219,60 @@ proto_again:
struct pppoe_hdr hdr;
__be16 proto;
} *hdr, _hdr;
u16 ppp_proto;
hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data, hlen, &_hdr);
if (!hdr) {
fdret = FLOW_DISSECT_RET_OUT_BAD;
break;
}
nhoff += PPPOE_SES_HLEN;
switch (hdr->proto) {
case htons(PPP_IP):
proto = htons(ETH_P_IP);
fdret = FLOW_DISSECT_RET_PROTO_AGAIN;
break;
case htons(PPP_IPV6):
proto = htons(ETH_P_IPV6);
fdret = FLOW_DISSECT_RET_PROTO_AGAIN;
break;
default:
if (!is_pppoe_ses_hdr_valid(hdr->hdr)) {
fdret = FLOW_DISSECT_RET_OUT_BAD;
break;
}
/* least significant bit of the most significant octet
* indicates if protocol field was compressed
*/
ppp_proto = ntohs(hdr->proto);
if (ppp_proto & 0x0100) {
ppp_proto = ppp_proto >> 8;
nhoff += PPPOE_SES_HLEN - 1;
} else {
nhoff += PPPOE_SES_HLEN;
}
if (ppp_proto == PPP_IP) {
proto = htons(ETH_P_IP);
fdret = FLOW_DISSECT_RET_PROTO_AGAIN;
} else if (ppp_proto == PPP_IPV6) {
proto = htons(ETH_P_IPV6);
fdret = FLOW_DISSECT_RET_PROTO_AGAIN;
} else if (ppp_proto == PPP_MPLS_UC) {
proto = htons(ETH_P_MPLS_UC);
fdret = FLOW_DISSECT_RET_PROTO_AGAIN;
} else if (ppp_proto == PPP_MPLS_MC) {
proto = htons(ETH_P_MPLS_MC);
fdret = FLOW_DISSECT_RET_PROTO_AGAIN;
} else if (ppp_proto_is_valid(ppp_proto)) {
fdret = FLOW_DISSECT_RET_OUT_GOOD;
} else {
fdret = FLOW_DISSECT_RET_OUT_BAD;
break;
}
if (dissector_uses_key(flow_dissector,
FLOW_DISSECTOR_KEY_PPPOE)) {
struct flow_dissector_key_pppoe *key_pppoe;
key_pppoe = skb_flow_dissector_target(flow_dissector,
FLOW_DISSECTOR_KEY_PPPOE,
target_container);
key_pppoe->session_id = hdr->hdr.sid;
key_pppoe->ppp_proto = htons(ppp_proto);
key_pppoe->type = htons(ETH_P_PPP_SES);
}
break;
}
case htons(ETH_P_TIPC): {