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FTP and SMTP share HTTP's line-based response-code-or-command shape
but keep their own command vocabularies in separate files rather than
sharing a parser. FTP passwords are shown as-is, not redacted - FTP
sends them in the clear regardless, matching Wireshark's own behavior.
TFTP is a small binary opcode protocol (RFC 1350) instead. IGMP sits
directly on IP like ICMP, so it's dispatched by protocol number rather
than through the port-keyed L7Registry the other three use.
Live-verified: FTP/SMTP against minimal real TCP servers written for
this (nothing installed locally), a full command/response exchange
decoded correctly in both directions. TFTP against a real atftpd
server and atftp client - the RRQ decoded correctly even though the
transfer itself didn't complete (an atftpd sandbox issue, not this
code). IGMP against real multicast traffic on wlp1s0, including a
genuine query from the actual router.
That live IGMP traffic caught a real bug before it shipped further:
parse_igmp() read bytes[4:8] as a group address for every message
type, but IGMPv3 reports use those bytes for Reserved+RecordCount
instead - a real V3 report showed "group=0.0.0.1" (0 reserved, 1
record, misread as an IP). Fixed by only populating group for the
types where it's genuinely an address; re-verified against the same
live traffic, and a regression test locks in the exact pattern.
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The single highest-value coverage gap so far, and structural rather
than a new dissector: a VLAN-tagged frame's ethertype reads as 0x8100,
so every existing decoder - ARP, IPv4, IPv6, and everything built on
top of them - was completely invisible on any tagged network.
walk_vlan_tags() (ethernet.hpp) is composable and separate from
parse_ethernet(), the same relationship walk_ipv6_extension_headers()
has to parse_ipv6(): the base parse stays an unconditional fixed-header
decode, and this is what a caller reaches for when it needs the real
protocol underneath. Handles stacked (QinQ) tags, bounded at 4 levels
against a corrupt/hostile frame claiming an unbounded chain.
Live-verified with genuine kernel-tagged frames, not synthetic bytes:
a dummy0 interface with an 802.1Q dummy0.42 sub-interface (VLAN 42),
captured on the parent while pinging out the sub-interface. Both
interfaces and the kernel modules they pulled in were torn down
afterward.
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NTP decodes the fixed header's version/mode/stratum - the timestamp
fields need NTP era/fraction fixed-point math to render meaningfully
and add nothing a one-line summary needs, so they're left alone.
DHCP decodes RFC 2131's BOOTP fixed header + magic cookie, then walks
the TLV options bounds-safely for option 53 (message type), plus
yiaddr when the server has assigned one. It's the first dissector
needing two well-known ports (67 server, 68 client) rather than one;
registering at just 67 still matches both directions since
l7_summarize() already falls back from dst_port to src_port.
Verified live: NTP against a real pool.ntp.org query on wlp1s0 (a
genuine stratum-2 reply came back). DHCP over loopback with a
synthetic-but-wire-format-real DISCOVER/OFFER exchange rather than a
real lease renewal, to avoid disrupting this machine's actual network
state - caught a test-setup mistake in the process (both packets
sent from the same ephemeral port instead of the OFFER actually
originating from port 67), not a dissector bug.
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ARP had zero treatment until now - its ethertype just fell through
summarize_packet's "not IPv4/IPv6" branch, on traffic that appears on
essentially every real LAN capture. Scoped to Ethernet/IPv4 addressing
(the case that covers virtually all real ARP traffic), with tcpdump's
own "who-has X tell Y" / "X is-at Y" phrasing rather than inventing
new wording. Live-verified by flushing this machine's real gateway
ARP entry and capturing the resulting request/reply on wlp1s0.
TUI -c/-a were being parsed into RenderOptions but silently did
nothing: run_tui()'s consumer thread had its own loop that never read
them, unlike plain-text mode's render_packet(). Fixed to match, and
caught a real bug while doing it - pushing up to two rows per packet
(summary + reassembly line) against a single pop_front() would let
the row deque grow past its cap under sustained -a activity; needed a
while loop instead. Verified under tmux against the same split-segment
HTTP scenario used to verify -a on the CLI and GUI.
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Decided on the name after weighing alternatives in NAMES.md: packeteer
(packet + -eer, "one who wields packets") fit the project's actual
scope better than the wire/frame pun once it had grown into full
L2-L7 dissection, reassembly, checksums, privilege dropping, and dual
TUI/GUI frontends. No existing packet-capture project uses the name;
the one real-world collision (Packeteer, Inc., a networking company
acquired and folded into Blue Coat/Symantec by 2008) is long defunct.
Mechanical rename throughout: CMake project/target names, the
wireframe:: namespace and include/wireframe/ directory (git mv,
history preserved), every #include path, CLI/GUI help text, and the
project's own working directory. NAMES.md rewritten to record the
decision instead of leaving stale self-referential etymology behind
from the blind rename pass.
Verified after every step: full rebuild (all four targets, no
warnings) and the full test suite (128/128 cases, 366/366 assertions)
both from a fresh reconfigure and again after the directory move.
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GUI parity: checksum_status()/reassembled_http_status() moved out of
main.cpp into a shared wireframe/packet_diagnostics.hpp so the GUI can
show the same -c/-a diagnostics for the selected packet without
duplicating the Ethernet/IPv4/TCP walk. Visually verified under Xvfb
with the same split-segment scenario used to verify -a on the CLI.
Two new L7 dissectors: mDNS (reuses parse_dns outright - RFC 6762
keeps DNS's wire format, just a different port) and SSH's cleartext
identification banner. Live-verified against this machine's real
sshd and a real DNS-wire-format packet sent to port 5353.
Two new fuzz harnesses (fuzz_checksum, fuzz_tcp_reassembly) covering
code added here that the original nine harnesses never
touched. All 12 run clean across ~90M executions with no crashes.
NAMES.md and PLAN.md updated with this round's decisions and naming
candidates.
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and TCP reassembly
Rounds out the build order in PLAN.md with six incremental additions:
drop root privileges immediately after opening the capture handle;
a standalone AF_PACKET/mmap ring-buffer demo (kept separate from
CaptureSession, see its header comment for why); ICMPv4/ICMPv6 type
and code decoding; opt-in IPv4/TCP/UDP checksum validation (-c);
CLI --help; and opt-in, in-order-only TCP stream reassembly (-a) so
HTTP requests/responses split across segments can be seen whole.
Each addition is unit-tested and, where it touches live traffic
behavior, verified against real captured packets - see PLAN.md's
Decisions section for the verification notes on each.
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Terminal packet capture and analysis tool built to learn the C++
memory model (byte layout, alignment, endianness, std::span over
unowned buffers) via a real capture pipeline.
- Hand-rolled L2-L4 decoders (Ethernet, IPv4, IPv6 with extension
header walking, TCP, UDP) over std::span, no struct-casting
- L7 dissector interface with DNS, HTTP, and TLS SNI implementations
- pcapng read/write for Wireshark-compatible capture files
- Bounded capture queue: drop-on-backpressure for live capture,
blocking push for faithful file replay
- Kernel-level BPF filtering (-f) and a separate display-only search
(-g / interactive) that doesn't touch what's captured
- Replay mode (-r) reads a saved pcapng file back through the same
pipeline as live capture, no root or live device needed
- pcap_stats() surfaces kernel/interface drops invisible to the
capture queue's own counter
- Three frontends sharing one CaptureSession setup path: CLI, TUI
(FTXUI, primary), GUI (Dear ImGui + SDL3, secondary)
- 89 unit tests (doctest) plus 9 libFuzzer harnesses covering every
hand-rolled parser; fuzzing found and fixed a real OOM in the
pcapng reader (unbounded allocation from an untrusted length field)
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