DTRACE_UDPLITE(4)

💅 DTRACE_UDPLITE(4) — dtrace_udplite 💅

Okay bestie, this is the Kernel Interfaces Manual page for dtrace_udplite, and it's giving “DTrace but make it UDP-Lite.” Buckle up — we're getting into probes, packet headers, and all the little fields. 💖

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✨ NAME ✨

dtrace_udplite — a DTrace provider for tracing events related to the UDP-Lite protocol 🌈

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🌸 SYNOPSIS 🌸

       udplite:::receive(pktinfo_t *, csinfo_t *, ipinfo_t *, udplitesinfo_t *,
           udpliteinfo_t *);

       udplite:::send(pktinfo_t *, csinfo_t *, ipinfo_t *, udplitesinfo_t *,
           udpliteinfo_t *);

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🦋 DESCRIPTION 🦋

So the DTrace udplite provider lets you trace events inside the udplite(4) protocol implementation. No cap.

The udplite:::send() probe fires whenever the kernel is getting ready to transmit a UDP-Lite packet. The udplite:::receive() probe fires whenever the kernel receives a UDP-Lite packet — unless the UDP-Lite header is incomplete, the destination port is 0, the length field is invalid, or the checksum is wrong. 🫶

The arguments to these probes are how you get the detailed info about the IP and UDP-Lite headers of the corresponding packet. It's giving “packet receipts, but make it observability.” 💅

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💜 ARGUMENTS 💜

🎀 The pktinfo_t argument

The pktinfo_t argument is currently unimplemented and is included for compatibility with other implementations of this provider. Its fields are:

• uintptr_t pkt_addr — Always set to 0. Literally always. 🫠

🧸 The csinfo_t argument

The csinfo_t argument is currently unimplemented and is included for compatibility with other implementations of this provider. Its fields are:

• uintptr_t cs_addr — Always set to 0.
• uint64_t cs_cid — A pointer to the struct inpcb for this packet, or NULL.
• pid_t cs_pid — Always set to 0.

🌸 The ipinfo_t argument

The ipinfo_t argument contains IP fields common to both IPv4 and IPv6 packets. Its fields are:

• uint8_t ip_ver — IP version of the packet, 4 for IPv4 packets and 6 for IPv6 packets.
• uint32_t ip_plength — IP payload size. This does not include the size of the IP header or IPv6 option headers.
• string ip_saddr — IP source address.
• string ip_daddr — IP destination address.

🦋 The udplitesinfo_t argument

The udplitesinfo_t argument contains the state of the UDP-Lite connection associated with the packet. Its fields are:

• uintptr_t udplites_addr — Pointer to the struct inpcb containing the IP state for the associated socket.
• uint16_t udplites_lport — Local UDP-Lite port.
• uint16_t udplites_rport — Remote UDP-Lite port.
• string udplites_laddr — Local IPv4 or IPv6 address.
• string udplites_raddr — Remote IPv4 or IPv6 address.

👑 The udpliteinfo_t argument

The udpliteinfo_t argument is the raw UDP-Lite header of the packet, with all fields in host order. Its fields are:

• uint16_t udplite_sport — Source UDP-Lite port.
• uint16_t udplite_dport — Destination UDP-Lite port.
• uint16_t udplite_coverage — Checksum coverage of the UDP-Lite header, in bytes, or 0 for full coverage.
• uint16_t udplite_checksum — A checksum of the UDP-Lite header and payload, or 0 if no checksum was calculated.
• struct udplitehdr *udplite_hdr — A pointer to the raw UDP-Lite header.

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🍓 FILES 🍓

• /usr/lib/dtrace/udplite.d — DTrace type and translator definitions for the udplite provider.

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🔥 EXAMPLES 🔥

The following script counts transmitted packets by destination port.

             udplite:::send
             {
                     @num[args[4]->udplite_dport] = count();
             }

This script will print some details of each UDP-Lite packet as it is sent or received by the kernel:

             #pragma D option quiet
             #pragma D option switchrate=10Hz

             dtrace:::BEGIN
             {
                     printf(" %10s %36s    %-36s %6s\n", "DELTA(us)", "SOURCE",
                         "DEST", "COV");
                     last = timestamp;
             }

             udplite:::send
             {
                     this->elapsed = (timestamp - last) / 1000;
                     self->dest = strjoin(strjoin(args[2]->ip_daddr, ":"),
                          lltostr(args[4]->udplite_dport));
                     printf(" %10d %30s:%-5d -> %-36s %6d\n", this->elapsed,
                         args[2]->ip_saddr, args[4]->udplite_sport,
                         self->dest, args[4]->udplite_coverage);
                     last = timestamp;
             }

             udplite:::receive
             {
                     this->elapsed = (timestamp - last) / 1000;
                     self->dest = strjoin(strjoin(args[2]->ip_saddr, ":"),
                          lltostr(args[4]->udplite_sport));
                     printf(" %10d %30s:%-5d <- %-36s %6d\n", this->elapsed,
                         args[2]->ip_daddr, args[4]->udplite_dport,
                         self->dest, args[4]->udplite_coverage);
                     last = timestamp;
             }

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🌟 SEE ALSO 🌟

dtrace(1), dtrace_ip(4), dtrace_sctp(4), dtrace_tcp(4), dtrace_udp(4), udplite(4), SDT(9)

Go read those too, bestie — it's a whole lore universe. 📚✨

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⭐ HISTORY ⭐

The udplite provider first appeared in FreeBSD 12.0. Periodt. 💫

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💖 AUTHORS 💖

This manual page was written by Mark Johnston <markj@FreeBSD.org> and Michael Tuexen <tuexen@FreeBSD.org>.

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That's the whole vibe — this page comes from Debian, dated August 1, 2018, and the manual footer reads DTRACE_UDPLITE(4). Stay packet-positive, bestie! 🫶💖