;; -*- tab-width: 4; -*-

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DEF Eth :=
	dst_mac := octets(6) format eth_addr
    src_mac := octets(6) format eth_addr
    ethtype := uint16 byteorder MSB format hex

DEF Eth := -- 802.1q
    dst_mac := octets(6) format eth_addr
    src_mac := octets(6) format eth_addr
    tpid := uint16 byteorder MSB format hex eq 8100
    tci := uint16 byteorder MSB is
    	vid := uint:12
        cfi := uint:1
        pcp := uint:3;
    ethtype := uint16 byteorder MSB format hex

DEF IPoEth :=
    Eth(ethtype eq 0800)
    IP_hdr

DEF IP_hdr (size = ihl*4) :=
    octet is
		ihl := uint:4
        ver := uint:4 eq 4;
    tos := uint8;
    total := uint16 byteorder msb
    id := uint16 byteorder msb
    uint16 byteorder msb is
		frag_offset := uint:13
        flags := uint:3 is
			mf := uint:1
            df := uint:1
    ttl := uint8
    proto := uint8
    hdr_csum := uint16 byteorder msb
    ip_src := octets(4) format ipv4
    ip_dst := octets(4) format ipv4
    options := fill IP_options

DEF IP_frag (size = total) :=
	IP_hdr
	IP_data := fill octets(..)

DEF IP := 
	FLOW(FORWARD(proto, ip_src, ip_dst), REVERSE(proto, ip_dst, ip_src))
	SEQ of IP_frag (id, proto, ip_src, ip_dst) => STREAM IP_data :=
		| mf eq 0, frag_offset eq 0 := IP_data
		| mf eq 1, frag_offset eq 0 [ offset = total ];
		  REPEAT (mf eq 1, frag_offset eq offset/8 [offset = offset + total]) ;
		  mf eq 0, frag_offset eq offset/8 := SEQ IP_data

DEF UDPoIP :=
    IP(proto eq 17)
    UDP

DEF UDP :=
	FLOW( REPLACE(IP), FORWARD(ip_src, ip_dst, sport, dport), REVERSE(ip_dst, ip_src, dport, sport))
    sport := uint16 byteorder msb
    dport := uint16 byteorder msb
    len := uint16 byteorder msb
    udpcsum := uint16 byteorder msb format hex
	UDP_data := fill octets(..)

DEF SIP_hdr := 
	UDP(dport def 5060)
	FLOW( REPLACE(UDP), FORWARD(ip_src, ip_dst, sport, dport, @SIP_headers{"Call-ID"})
		  REVERSE(ip_dst, ip_src, dport, sport, @SIP_headers{"Call-ID"}) )
	REGEXP SIP_method (?<SIP_addr>\S+) SIP/2.0\n
	REPEAT SIP_headers{SIP_header => SIP_value} (REGEXP (?<SIP_header>\S+): (?<SIP_value>.+)\n)
	"\n"

DEF SIP_method := 
	SIP_method | "INVITE"

DEF SIP_SDP :=
	SIP_hdr(@SIP_headers{"Content-Type"} eq "application/sdp")
	REPEAT SDP_DESCR

DEF SDP_DESCR :=
	FLOW( SUBORDINATE, ID(SDP_opts{"o"}), FORWARD(ip_src eq  ?, ip_dst eq SDP_opts{"c"}(IP), sport eq ?, dport eq SDP_opts{"m"}(port), proto udp))
	REGEXP v=\d+\n
	REPEAT SDP_opts{SDP_opt => SDP_val} (REGEXP (?<SDP_opt>\S)=(?<SDP_val>.+)\n)
	
DEF SDP_opts("c") :=
	REGEXP IN IP4 (?<IP>.+)

DEF SDP_opts("m") :=
	REGEXP (?<media>\S+) (?<port>\d+) (?<proto>\S+) .+