Add FTP, SMTP, TFTP, and IGMP; fix an IGMPv3 group-address misparse

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.

1 files changed, 85 insertions, 0 deletions

diff --git a/tests/test_tftp.cpp b/tests/test_tftp.cpp
new file mode 100644
index 0000000..2955537
--- /dev/null
+++ b/tests/test_tftp.cpp
@@ -0,0 +1,85 @@
+#include <doctest/doctest.h>
+
+#include <vector>
+
+#include "packeteer/l7/tftp.hpp"
+
+using namespace packeteer::net;
+
+namespace {
+
+std::vector<unsigned char> build_rrq(const std::string& filename, const std::string& mode) {
+    std::vector<unsigned char> bytes = {0x00, 0x01};  // opcode RRQ
+    bytes.insert(bytes.end(), filename.begin(), filename.end());
+    bytes.push_back(0);
+    bytes.insert(bytes.end(), mode.begin(), mode.end());
+    bytes.push_back(0);
+    return bytes;
+}
+
+}  // namespace
+
+TEST_CASE("parse_tftp decodes an RRQ with filename and mode") {
+    auto msg = parse_tftp(build_rrq("boot.img", "octet"));
+    REQUIRE(msg.has_value());
+    CHECK(msg->opcode == kTftpRrq);
+    REQUIRE(msg->filename.has_value());
+    CHECK(*msg->filename == "boot.img");
+    REQUIRE(msg->mode.has_value());
+    CHECK(*msg->mode == "octet");
+}
+
+TEST_CASE("parse_tftp decodes a DATA block number") {
+    std::vector<unsigned char> bytes = {0x00, 0x03, 0x00, 0x07, 'h', 'i'};
+    auto msg = parse_tftp(bytes);
+    REQUIRE(msg.has_value());
+    CHECK(msg->opcode == kTftpData);
+    REQUIRE(msg->block.has_value());
+    CHECK(*msg->block == 7);
+}
+
+TEST_CASE("parse_tftp decodes an ACK block number") {
+    std::vector<unsigned char> bytes = {0x00, 0x04, 0x00, 0x07};
+    auto msg = parse_tftp(bytes);
+    REQUIRE(msg.has_value());
+    CHECK(msg->opcode == kTftpAck);
+    REQUIRE(msg->block.has_value());
+    CHECK(*msg->block == 7);
+}
+
+TEST_CASE("parse_tftp decodes an ERROR code and message") {
+    std::vector<unsigned char> bytes = {0x00, 0x05, 0x00, 0x01};
+    std::string message = "File not found";
+    bytes.insert(bytes.end(), message.begin(), message.end());
+    bytes.push_back(0);
+
+    auto msg = parse_tftp(bytes);
+    REQUIRE(msg.has_value());
+    CHECK(msg->opcode == kTftpError);
+    REQUIRE(msg->error_code.has_value());
+    CHECK(*msg->error_code == 1);
+    REQUIRE(msg->error_message.has_value());
+    CHECK(*msg->error_message == "File not found");
+}
+
+TEST_CASE("parse_tftp rejects an opcode outside the known range") {
+    std::vector<unsigned char> bytes = {0x00, 0x99};
+    CHECK_FALSE(parse_tftp(bytes).has_value());
+}
+
+TEST_CASE("parse_tftp handles an RRQ with a truncated filename gracefully") {
+    std::vector<unsigned char> bytes = {0x00, 0x01, 'a', 'b'};  // no null terminator
+    auto msg = parse_tftp(bytes);
+    REQUIRE(msg.has_value());
+    CHECK(msg->opcode == kTftpRrq);
+    CHECK_FALSE(msg->filename.has_value());
+}
+
+TEST_CASE("TftpDissector claims port 69 and formats an RRQ") {
+    TftpDissector dissector;
+    CHECK(dissector.port() == kTftpPort);
+
+    auto summary = dissector.summarize(build_rrq("boot.img", "octet"));
+    REQUIRE(summary.has_value());
+    CHECK(*summary == "TFTP RRQ boot.img (octet)");
+}