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DTRACE_UDP(4) Device Drivers Manual DTRACE_UDP(4)

dtrace_udp — a DTrace provider for tracing events related to the UDP protocol

udp:::receive(pktinfo_t *, csinfo_t *, ipinfo_t *, udpsinfo_t *, udpinfo_t *);

udp:::send(pktinfo_t *, csinfo_t *, ipinfo_t *, udpsinfo_t *, udpinfo_t *);

The DTrace udp provider allows users to trace events in the udp(4) protocol implementation. The () probe fires whenever the kernel prepares to transmit a UDP packet, and the () probe fires whenever the kernel receives a UDP packet, unless the UDP header is incomplete, the destination port is 0, the length field is invalid, or the checksum is wrong. The arguments to these probes can be used to obtain detailed information about the IP and UDP headers of the corresponding packet.

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.

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 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 udpsinfo_t argument contains the state of the UDP connection associated with the packet. Its fields are:

uintptr_t udps_addr
Pointer to the struct inpcb containing the IP state for the associated socket.
uint16_t udps_lport
Local UDP port.
uint16_t udps_rport
Remote UDP port.
string udps_laddr
Local IPv4 or IPv6 address.
string udps_raddr
Remote IPv4 or IPv6 address.

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

uint16_t udp_sport
Source UDP port.
uint16_t udp_dport
Destination UDP port.
uint16_t udp_length
Length of the UDP header and payload, in bytes.
uint16_t udp_checksum
A checksum of the UDP header and payload, or 0 if no checksum was calculated.
struct udphdr *udp_hdr
A pointer to the raw UDP header.

/usr/lib/dtrace/udp.d
DTrace type and translator definitions for the udp provider.

The following script counts transmitted packets by destination port.

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

This script will print some details of each UDP 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", "BYTES");
        last = timestamp;
}

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

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

This provider is compatible with the udp provider in Solaris.

dtrace(1), dtrace_ip(4), dtrace_sctp(4), dtrace_tcp(4), dtrace_udplite(4), udp(4), SDT(9)

The udp provider first appeared in FreeBSD 10.0.

This manual page was written by Mark Johnston <markj@FreeBSD.org>.

August 1, 2018 FreeBSD-12.0