FrameAssembly (.fasm Packet Crafting DSL) Support (v1.4.2)

Comprehensive syntax highlighting, 16 tab-completable snippets, and language tooling for FrameAssembly (.fasm, text/vnd.frameassembly) network packet specifications in Visual Studio Code, Cursor, Windsurf, VSCodium, and Antigravity IDE.

Example .fasm Workflows

Create a Custom .pcap Capture from Plain Text (No Root or Python)

Write a declarative .fasm recipe with automatic RFC checksums and compile it in unprivileged user space—without Python Scapy scripts, CAP_NET_RAW root permissions, or raw hexadecimal byte offsets in text2pcap:

HOST client { IP 192.168.1.100 }
HOST server { IP 8.8.8.8 }

FLOW dns_resolve(c, s) {
    c -> s DNS QUERY TXID 0x1a2b QNAME "example.com" QTYPE "A"
    c <- s DNS RESPONSE TXID 0x1a2b QNAME "example.com" QTYPE "A" RDATA "93.184.216.34"
}

COMPILE {
    dns_resolve(client, server)
}

$ frameassembly dns.fasm -o dns.pcap

Test SNMPv1/v2c & Encrypted SNMPv3 authPriv Trap Receivers

FrameAssembly handles RFC 3414/3826/7860 key derivation (Ku -> Kul), localized auth HMACs, and DES-CBC/AES-128-CFB encryption automatically with zero manual ASN.1 math:

HOST router { IP 10.151.0.1 }
HOST soc    { IP 10.151.0.250 }

FLOW snmpv3_trap(r, s) {
    r -> s SNMP3 TRAP USER "admin" ENGINEID "80001f8880510001" AUTH SHA256 "authpass123" PRIV AES "privpass123" OID 1.3.6.1.6.3.1.1.5.3
}

COMPILE {
    snmpv3_trap(router, soc)
}

$ frameassembly trap.fasm -o trap.pcap && tcpreplay -i eth0 trap.pcap

Craft 802.1Q VLAN, 802.1ad QinQ, MPLS & DSCP QoS Packets

Write inner and outer VLAN tags, MPLS labels, and DSCP priority fields directly into the .pcap file without OS NIC drivers stripping VLAN tags:

HOST hub    { IP 10.99.1.1 }
HOST branch { IP 10.99.1.2 }

FLOW qinq_flow(h, b) {
    h -> b QINQ 850 INNER_VLAN 12 ICMP ECHO_REQUEST
    h <- b QINQ 850 INNER_VLAN 12 ICMP ECHO_REPLY
}

COMPILE {
    qinq_flow(hub, branch)
}

$ frameassembly trunk.fasm -o trunk.pcap && tshark -r trunk.pcap -V

Features

• 81 Native Protocols: Complete syntax highlighting for all 81 Layer 2, Layer 3, Layer 4, and Layer 7 protocols (including Ethernet, VLAN, QinQ, MPLS, IPv4, IPv6, ICMP, NDP, GRE, VXLAN, IPsec, OSPF, BGP, TCP, UDP, SCTP, SNMPv1/v2c/v3, DNS, HTTP, TLS, QUIC, Modbus, BACnet, S7comm, and more).
• 16 Built-In Tab-Completable Snippets: Instant templates for complete .fasm programs (fasm-skeleton, fasm-tcp-http, fasm-snmpv3, fasm-vlan, fasm-qinq, fasm-dns, fasm-dhcp, fasm-icmp, fasm-arp, fasm-bgp, fasm-ospf, fasm-vxlan, fasm-wireguard, fasm-modbus, fasm-syslog) plus individual host, flow, and compile blocks.
• Comprehensive Modifiers & Sub-Keywords: Full coverage of over 180 protocol sub-keywords, frame modifiers (VLAN PCP/DEI, MPLS EXP/BOS/TTL, IPv4/IPv6 TTL, DSCP, ECN, Flow Labels, fragmentation, TCP options, SCTP chunks).
• Dual-Stack & Multi-Format MAC Addressing: Native highlighting for IPv4 dotted-quads, full/compressed/mapped IPv6 addresses, and colon-separated (00:1a:2b:3c:4d:5e), hyphen-separated (00-1A-2B-3C-4D-5E), and Cisco IOS dotted-quad (001a.2b3c.4d5e) MAC addresses.
• Timing & Numeric Formats: Support for duration units (ns, us, ms, s, m), hexadecimal integer literals (0x...), and dotted SNMP OID notation.
• Language Structure: Distinct styling for structural declarations (HOST, FLOW, COMPILE, LOOP), transmission direction arrows (->, <-), and quoted string payloads.
• Standardized MIME & Scope: Bound to the official text/vnd.frameassembly media type and source.frameassembly TextMate scope.

Usage

Open any .fasm file in VS Code, Cursor, Windsurf, VSCodium, or Antigravity IDE. The extension activates automatically and applies the source.frameassembly TextMate grammar and snippets.

To install both the frameassembly CLI compiler and this editor extension in a single command (without cloning the repository):

curl -fsSL https://raw.githubusercontent.com/SteveWinschel/FrameAssembly/main/install.sh | sh

Or install the CLI compiler directly via Cargo and compile .fasm files into .pcap captures:

cargo install frameassembly
frameassembly show capture.fasm
frameassembly capture.fasm -o output.pcap

License

MIT License. Copyright (c) 2026 Steve Winschel.