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.Dd April 18, 2015
.Dt DTRACE_UDP 4
.Os
.Sh NAME
.Nm dtrace_udp
.Nd a DTrace provider for tracing events related to the UDP protocol
.Sh SYNOPSIS
.Fn udp:::receive "pktinfo_t *" "csinfo_t *" "ipinfo_t *" "udpsinfo_t *" \
    "udpinfo_t *"
.Fn udp:::send "pktinfo_t *" "csinfo_t *" "ipinfo_t *" "udpsinfo_t *" \
    "udpinfo_t *"
.Sh DESCRIPTION
The DTrace
.Nm udp
provider allows users to trace events in the
.Xr udp 4
protocol implementation.
The
.Fn udp:::send
probe fires whenever the kernel prepares to transmit a UDP packet, and the
.Fn udp:::receive
probe fires whenever the kernel receives a UDP packet.
The arguments to these probes can be used to obtain detailed information about
the IP and UDP headers of the corresponding packet.
.Sh ARGUMENTS
The
.Vt pktinfo_t
argument is currently unimplemented and is included for compatibility with other
implementations of this provider.
Its fields are:
.Bl -tag -width "uintptr_t pkt_addr" -offset indent
.It Vt uintptr_t pkt_addr
Always set to 0.
.El
.Pp
The
.Vt csinfo_t
argument is currently unimplemented and is included for compatibility with other
implementations of this provider.
Its fields are:
.Bl -tag -width "uintptr_t cs_addr" -offset indent
.It Vt uintptr_t cs_addr
Always set to 0.
.It Vt uint64_t cs_cid
A pointer to the
.Vt struct inpcb
for this packet, or
.Dv NULL .
.It Vt pid_t cs_pid
Always set to 0.
.El
.Pp
The
.Vt ipinfo_t
argument contains IP fields common to both IPv4 and IPv6 packets.
Its fields are:
.Bl -tag -width "uint32_t ip_plength" -offset indent
.It Vt uint8_t ip_ver
IP version of the packet, 4 for IPv4 packets and 6 for IPv6 packets.
.It Vt uint32_t ip_plength
IP payload size.
This does not include the size of the IP header or IPv6 option headers.
.It Vt string ip_saddr
IP source address.
.It Vt string ip_daddr
IP destination address.
.El
.Pp
The
.Vt udpsinfo_t
argument contains the state of the UDP connection associated with the packet.
Its fields are:
.Bl -tag -width "uintptr_t udps_addr" -offset indent
.It Vt uintptr_t udps_addr
Pointer to the
.Vt struct inpcb
containing the IP state for the associated socket.
.It Vt uint16_t udps_lport
Local UDP port.
.It Vt uint16_t udps_rport
Remote UDP port.
.It Vt string udps_laddr
Local IPv4 or IPv6 address.
.It Vt string udps_raddr
Remote IPv4 or IPv6 address.
.El
.Pp
The
.Vt udpinfo_t
argument is the raw UDP header of the packet, with all fields in host order.
Its fields are:
.Bl -tag -width "struct udphdr *udp_hdr" -offset indent
.It Vt uint16_t udp_sport
Source UDP port.
.It Vt uint16_t udp_dport
Destination UDP port.
.It Vt uint16_t udp_length
Length of the UDP header and payload, in bytes.
.It Vt uint16_t udp_checksum
A checksum of the UDP header and payload, or 0 if no checksum was calculated.
.It Vt struct udphdr *udp_hdr
A pointer to the raw UDP header.
.El
.Sh FILES
.Bl -tag -width "/usr/lib/dtrace/udp.d" -compact
.It Pa /usr/lib/dtrace/udp.d
DTrace type and translator definitions for the
.Nm udp
provider.
.El
.Sh EXAMPLES
The following script counts transmitted packets by destination port.
.Bd -literal -offset indent
udp:::send
{
        @num[args[4]->udp_dport] = count();
}
.Ed
.Pp
This script will print some details of each UDP packet as it is sent or received
by the kernel:
.Bd -literal -offset indent
#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;
}
.Ed
.Sh COMPATIBILITY
This provider is compatible with the
.Nm udp
provider in Solaris.
.Sh SEE ALSO
.Xr dtrace 1 ,
.Xr dtrace_ip 4 ,
.Xr dtrace_tcp 4 ,
.Xr udp 4 ,
.Xr SDT 9
.Sh HISTORY
The
.Nm udp
provider first appeared in
.Fx
10.0.
.Sh AUTHORS
This manual page was written by
.An Mark Johnston Aq Mt markj@FreeBSD.org .