DTRACE_UDPLITE(4)

💖 NAME 💖

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

okay bestie so this is a section 4 page from the Kernel Interfaces Manual, and it's literally all about the DTrace provider that lets you peek at UDP-Lite stuff happening in the kernel ✨

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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 🦋

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. 🙈 (sorry bestie, those ones just don't make it to the probe)

The arguments to these probes are your besties for getting super detailed info about the IP and UDP-Lite headers of the packet in question. it's giving forensic scientist 🔍

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✨ ARGUMENTS ✨

🌸 pktinfo_t

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

• uintptr_t pkt_addr — always set to 0.

🌸 csinfo_t

The csinfo_t argument is also currently unimplemented and likewise just there 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.

🌸 ipinfo_t

The ipinfo_t argument carries the IP fields that are 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. Heads up: 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.

🌸 udplitesinfo_t

The udplitesinfo_t argument holds 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.

🌸 udpliteinfo_t

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. the blueprint, fr fr 🧚

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💜 EXAMPLES 💜

This lil script right here counts transmitted packets by destination port. iconic behaviour:

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

And this one prints some details of every UDP-Lite packet as it's 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)

like, go read those too, they're all in the same friend group 💖

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📜 HISTORY 📜

The udplite provider first appeared in FreeBSD 12.0. a whole era ✨

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🫶 AUTHORS 🫶

This manual page was written by Mark Johnston <markj@FreeBSD.org> and Michael Tuexen <tuexen@FreeBSD.org>. absolute legends, no notes 💅

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and that's the whole page, bestie!! 🦋 this one shipped from Debian, dated August 1, 2018, and it lives in the manual as DTRACE_UDPLITE(4). mwah, slay, periodt 💖🎀🌸