Add support for B.A.T.M.A.N. Advanced

This adds support for the layer 2 mesh routing protocol
B.A.T.M.A.N. Advanced. "batadv" can be used to filter on batman-adv
packets. It also allows later filters to look at frames inside the
tunnel when both "version" and "type" are specified.

Documentation for the batman-adv protocol can be found at the following
locations:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/batman-adv.rst
https://www.open-mesh.org/

Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>

Makefile.in

@@ -121,6 +121,8 @@ PUBHDR = \
 HDR = $(PUBHDR) \
 	arcnet.h \
 	atmuni31.h \
+	batadv_legacy_packet.h \
+	batadv_packet.h \
 	diag-control.h \
 	ethertype.h \
 	extract.h \

batadv_legacy_packet.h

@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: BSD-3 */
+/* Copyright (C) 2020  Linus Lüssing */
+
+#ifndef _BATADV_LEGACY_PACKET_H_
+#define _BATADV_LEGACY_PACKET_H_
+
+enum batadv_legacy_packettype {
+	BATADV_LEGACY_IV_OGM		= 0x01,
+	BATADV_LEGACY_ICMP		= 0x02,
+	BATADV_LEGACY_UNICAST		= 0x03,
+	BATADV_LEGACY_BCAST		= 0x04,
+	BATADV_LEGACY_VIS		= 0x05,
+	BATADV_LEGACY_UNICAST_FRAG	= 0x06,
+	BATADV_LEGACY_TT_QUERY		= 0x07,
+	BATADV_LEGACY_ROAM_ADV		= 0x08,
+	BATADV_LEGACY_UNICAST_4ADDR	= 0x09,
+	BATADV_LEGACY_CODED		= 0x0a,
+};
+
+#define ETH_ALEN	6
+
+struct batadv_legacy_unicast_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t ttvn;
+	uint8_t dest[ETH_ALEN];
+};
+
+struct batadv_legacy_unicast_4addr_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t src[ETH_ALEN];
+	uint8_t subtype;
+	uint8_t reserved;
+};
+
+struct batadv_legacy_unicast_frag_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t ttvn;
+	uint8_t dest[ETH_ALEN];
+	uint8_t flags;
+	uint8_t align;
+	uint8_t orig[ETH_ALEN];
+	uint8_t seqno[2];		/* 2-byte integral value */
+};
+
+struct batadv_legacy_bcast_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t reserved;
+	uint8_t seqno[4];		/* 4-byte integral value */
+	uint8_t orig[ETH_ALEN];
+};
+
+struct batadv_legacy_coded_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t first_ttvn;
+	uint8_t first_source[ETH_ALEN];
+	uint8_t first_orig_dest[ETH_ALEN];
+	uint8_t first_crc[4];		/* 4-byte integral value */
+	uint8_t second_ttl;
+	uint8_t second_ttvn;
+	uint8_t second_dest[ETH_ALEN];
+	uint8_t second_source[ETH_ALEN];
+	uint8_t second_orig_dest[ETH_ALEN];
+	uint8_t second_crc[4];		/* 4-byte integral value */
+	uint8_t coded_len[2];		/* 2-byte integral value */
+};
+
+#endif /* _BATADV_LEGACY_PACKET_H_ */

batadv_packet.h

@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: BSD-3 */
+/* Copyright (C) 2024  Linus Lüssing */
+
+#ifndef _BATADV_PACKET_H_
+#define _BATADV_PACKET_H_
+
+/* For the definitive and most recent packet format definition,
+ * see the batadv_packet.h in the Linux kernel.
+ */
+
+enum batadv_packettype {
+	BATADV_IV_OGM           = 0x00,
+	BATADV_BCAST            = 0x01,
+	BATADV_CODED            = 0x02,
+	BATADV_ELP		= 0x03,
+	BATADV_OGM2		= 0x04,
+	BATADV_MCAST		= 0x05,
+	BATADV_UNICAST          = 0x40,
+	BATADV_UNICAST_FRAG     = 0x41,
+	BATADV_UNICAST_4ADDR    = 0x42,
+	BATADV_ICMP             = 0x43,
+	BATADV_UNICAST_TVLV     = 0x44,
+};
+
+#define ETH_ALEN	6
+
+struct batadv_unicast_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t ttvn;
+	uint8_t dest[ETH_ALEN];
+};
+
+struct batadv_unicast_4addr_packet {
+	struct batadv_unicast_packet u;
+	uint8_t src[ETH_ALEN];
+	uint8_t subtype;
+	uint8_t reserved;
+};
+
+struct batadv_frag_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t num_pri;	/* number and priority */
+	uint8_t dest[ETH_ALEN];
+	uint8_t orig[ETH_ALEN];
+	uint8_t seqno[2];	/* 2-byte integral value */
+	uint8_t total_size[2];	/* 2-byte integral value */
+};
+
+struct batadv_bcast_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t reserved;
+	uint8_t seqno[4];	/* 4-byte integral value */
+	uint8_t orig[ETH_ALEN];
+};
+
+struct batadv_coded_packet {
+	uint8_t packet_type;
+	uint8_t version;
+	uint8_t ttl;
+	uint8_t first_ttvn;
+	uint8_t first_source[ETH_ALEN];
+	uint8_t first_orig_dest[ETH_ALEN];
+	uint8_t first_crc[4];	/* 4-byte integral value */
+	uint8_t second_ttl;
+	uint8_t second_ttvn;
+	uint8_t second_dest[ETH_ALEN];
+	uint8_t second_source[ETH_ALEN];
+	uint8_t second_orig_dest[ETH_ALEN];
+	uint8_t second_crc[4];	/* 4-byte integral value */
+	uint8_t coded_len[2];	/* 2-byte integral value */
+};
+
+#endif /* _BATADV_PACKET_H_ */

ethertype.h

@@ -49,6 +49,9 @@
 #ifndef ETHERTYPE_TRAIL
 #define ETHERTYPE_TRAIL		0x1000
 #endif
+#ifndef ETHERTYPE_BATMAN
+#define ETHERTYPE_BATMAN	0x4305 /* B.A.T.M.A.N. Advanced */
+#endif
 #ifndef	ETHERTYPE_MOPDL
 #define ETHERTYPE_MOPDL		0x6001
 #endif

gencode.c

@@ -54,6 +54,8 @@
 #include "sunatmpos.h"
 #include "pflog.h"
 #include "ppp.h"
+#include "batadv_packet.h"
+#include "batadv_legacy_packet.h"
 #include "pcap/sll.h"
 #include "pcap/ipnet.h"
 #include "arcnet.h"
@@ -9951,6 +9953,169 @@ gen_vxlan(compiler_state_t *cstate, bpf_u_int32 vni, int has_vni)
 	return b1;
 }
 
+static struct block *
+gen_batadv_check_version(compiler_state_t *cstate, struct block *b0, bpf_u_int32 version)
+{
+	struct block *b1;
+
+	if (version > UINT8_MAX)
+		bpf_error(cstate,
+			  "batman-adv compatibility version number %u unsupported",
+			  version);
+
+	b1 = gen_cmp(cstate, OR_LINKPL, 1, BPF_B, version);
+	gen_and(b0, b1);
+
+	return b1;
+}
+
+static struct block *
+gen_batadv_check_type(compiler_state_t *cstate, struct block *b0,
+		      bpf_u_int32 version, bpf_u_int32 type)
+{
+	struct block *b1;
+
+	switch (version) {
+	case 14:
+	case 15:
+		if (type > UINT8_MAX)
+			bpf_error(cstate,
+				  "batman-adv packet type %u unsupported for compatibility version %u",
+				  type, version);
+
+		b1 = gen_cmp(cstate, OR_LINKPL, 0, BPF_B, type);
+		gen_and(b0, b1);
+		b0 = b1;
+
+		break;
+	default:
+		bpf_error(cstate,
+			  "batman-adv compatibility version number %u unsupported",
+			  version);
+	}
+
+	return b0;
+}
+
+
+static void gen_batadv_push_offset(compiler_state_t *cstate, u_int offset)
+{
+	PUSH_LINKHDR(cstate, DLT_EN10MB, cstate->off_linkpl.is_variable,
+		     cstate->off_linkpl.constant_part + cstate->off_nl + offset,
+		     cstate->off_linkpl.reg);
+
+	cstate->off_linktype.constant_part += cstate->off_linkhdr.constant_part;
+	cstate->off_linkpl.constant_part += cstate->off_linkhdr.constant_part;
+
+	cstate->off_nl = 0;
+	cstate->off_nl_nosnap = 0;	/* no 802.2 LLC */
+}
+
+static void
+gen_batadv_offsets_v14(compiler_state_t *cstate, bpf_u_int32 type)
+{
+	size_t offset;
+
+	switch (type) {
+	case BATADV_LEGACY_UNICAST:		/* 0x03 */
+		offset = sizeof(struct batadv_legacy_unicast_packet);
+		break;
+	case BATADV_LEGACY_BCAST:		/* 0x04 */
+		offset = sizeof(struct batadv_legacy_bcast_packet);
+		break;
+	case BATADV_LEGACY_UNICAST_FRAG:	/* 0x06 */
+		offset = sizeof(struct batadv_legacy_unicast_frag_packet);
+		break;
+	case BATADV_LEGACY_UNICAST_4ADDR:	/* 0x09 */
+		offset = sizeof(struct batadv_legacy_unicast_4addr_packet);
+		break;
+	case BATADV_LEGACY_CODED:		/* 0x0a */
+		offset = sizeof(struct batadv_legacy_coded_packet);
+		break;
+	default:
+		offset = 0;
+	}
+
+	if (offset)
+		gen_batadv_push_offset(cstate, (u_int)offset);
+}
+
+static void
+gen_batadv_offsets_v15(compiler_state_t *cstate, bpf_u_int32 type)
+{
+	size_t offset;
+
+	switch (type) {
+	case BATADV_BCAST:		/* 0x01 */
+		offset = sizeof(struct batadv_bcast_packet);
+		break;
+	case BATADV_CODED:		/* 0x02 */
+		offset = sizeof(struct batadv_coded_packet);
+		break;
+	case BATADV_UNICAST:		/* 0x40 */
+		offset = sizeof(struct batadv_unicast_packet);
+		break;
+	case BATADV_UNICAST_FRAG:	/* 0x41 */
+		offset = sizeof(struct batadv_frag_packet);
+		break;
+	case BATADV_UNICAST_4ADDR:	/* 0x42 */
+		offset = sizeof(struct batadv_unicast_4addr_packet);
+		break;
+	case BATADV_MCAST:		/* 0x05 */
+	case BATADV_UNICAST_TVLV:	/* 0x44 */
+		/* unsupported for now, needs variable offset to
+		 * take tvlv_len into account
+		 */
+		/* fall through */
+	default:
+		offset = 0;
+	}
+
+	if (offset)
+		gen_batadv_push_offset(cstate, (u_int)offset);
+}
+
+static void
+gen_batadv_offsets(compiler_state_t *cstate, bpf_u_int32 version, bpf_u_int32 type)
+{
+	switch (version) {
+	case 14:
+		gen_batadv_offsets_v14(cstate, type);
+		break;
+	case 15:
+		gen_batadv_offsets_v15(cstate, type);
+		break;
+	default:
+		break;
+	}
+}
+
+struct block *
+gen_batadv(compiler_state_t *cstate, bpf_u_int32 version, int has_version,
+	   bpf_u_int32 type, int has_type)
+{
+	struct block *b0;
+
+	/*
+	 * Catch errors reported by us and routines below us, and return NULL
+	 * on an error.
+	 */
+	if (setjmp(cstate->top_ctx))
+		return (NULL);
+
+	b0 = gen_linktype(cstate, ETHERTYPE_BATMAN);
+
+	if (has_version)
+		b0 = gen_batadv_check_version(cstate, b0, version);
+
+	if (has_type) {
+		b0 = gen_batadv_check_type(cstate, b0, version, type);
+		gen_batadv_offsets(cstate, version, type);
+	}
+
+	return b0;
+}
+
 /* Check that the encapsulated frame has a link layer header
  * for Ethernet filters. */
 static struct block *

gencode.h

@@ -359,6 +359,9 @@ struct block *gen_pppoes(compiler_state_t *, bpf_u_int32, int);
 struct block *gen_geneve(compiler_state_t *, bpf_u_int32, int);
 struct block *gen_vxlan(compiler_state_t *, bpf_u_int32, int);
 
+struct block *gen_batadv(compiler_state_t *, bpf_u_int32, int,
+			 bpf_u_int32, int);
+
 struct block *gen_atmfield_code(compiler_state_t *, int, bpf_u_int32,
     int, int);
 struct block *gen_atmtype_abbrev(compiler_state_t *, int);