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				.Dd May 4, 2018
				.Dt NETDUMP 4
				.Os
				.Sh NAME
				.Nm netdump
				.Nd protocol for transmitting kernel dumps to a remote server
				.Sh SYNOPSIS
				To compile netdump client support into the kernel, place the following line in
				your kernel configuration file:
				.Bd -ragged -offset indent
				.Cd "options NETDUMP"
				.Ed
				.Pp
				Debug output can be enabled by adding the following line:
				.Bd -ragged -offset indent
				.Cd "options NETDUMP_DEBUG"
				.Ed
				.Sh DESCRIPTION
				netdump is a UDP-based protocol for transmitting kernel dumps to a remote host.
				A netdump client is a panicking kernel, and a netdump server is a host
				running the
				.Nm
				daemon, available in ports as
				.Pa ports/ftp/netdumpd .
				.Nm
				clients are configured using the
				.Xr dumpon 8
				utility.
				.Pp
				.Nm
				client messages consist of a fixed-size header followed by a variable-sized
				payload.
				The header contains the message type, a sequence number, the offset of
				the payload data in the kernel dump, and the length of the payload data
				(not including the header).
				The message types are
				.Dv HERALD , FINISHED , KDH , VMCORE ,
				and
				.Dv EKCD_KEY .
				.Nm
				server messages have a fixed size and contain only the sequence number of
				the client message.
				These messages indicate that the server has successfully processed the
				client message with the corresponding sequence number.
				All client messages are acknowledged this way.
				Server messages are always sent to port 20024 of the client.
				.Pp
				To initiate a
				.Nm ,
				the client sends a
				.Dv HERALD
				message to the server at port 20023.
				The client may include a relative path in its payload, in which case the
				.Nm
				server should attempt to save the dump at that path relative to its configured
				dump directory.
				The server will acknowledge the
				.Dv HERALD
				using a random source port, and the client must send all subsequent messages
				to that port.
				.Pp
				The
				.Dv KDH , VMCORE ,
				and
				.Dv EKCD_KEY
				message payloads contain the kernel dump header, dump contents, and
				dump encryption key respectively.
				The offset in the message header should be treated as a seek offset
				in the corresponding file.
				There are no ordering requirements for these messages.
				.Pp
				A
				.Nm
				is completed by sending the
				.Dv FINISHED
				message to the server.
				.Pp
				The following network drivers support netdump:
				.Xr alc 4 ,
				.Xr bge 4 ,
				.Xr bxe 4 ,
				.Xr cxgb 4 ,
				.Xr em 4 ,
				.Xr igb 4 ,
				.Xr ix 4 ,
				.Xr mlx4en 4 ,
				.Xr re 4 ,
				.Xr vtnet 4 .
				.Sh SEE ALSO
				.Xr decryptcore 8 ,
				.Xr dumpon 8 ,
				.Xr savecore 8
				.Sh HISTORY
				.Nm
				client support first appeared in
				.Fx 12.0 .
				.Sh BUGS
				Only IPv4 is supported.
				.Pp
				.Nm
				may only be used after the kernel has panicked.