freebsd/share/man/man9/domain.9

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.Dd December 7, 2001
.Dt DOMAIN 9
.Os
.Sh NAME
.Nm net_add_domain ,
.Nm pfctlinput ,
.Nm pfctlinput2 ,
.Nm pffindproto ,
.Nm pffindtype ,
.Nm DOMAIN_SET
.Nd "network domain management"
.Sh SYNOPSIS
.In sys/param.h
.In sys/kernel.h
.In sys/protosw.h
.In sys/domain.h
.Ft void
.Fn net_add_domain "void *data"
.Ft void
.Fn pfctlinput "int cmd" "struct sockaddr *sa"
.Ft void
.Fn pfctlinput2 "int cmd" "struct sockaddr *sa" "void *ctlparam"
.Ft struct protosw *
.Fn pffindproto "int family" "int protocol" "int type"
.Ft struct protosw *
.Fn pffindtype "int family" "int type"
.Ft void
.Fn DOMAIN_SET "name"
.Sh DESCRIPTION
Network protocols installed in the system are maintained within what
are called domains
(for example the
.Va inetdomain
and
.Va localdomain ) .
.Bd -literal
struct domain {
	int	dom_family;		/* AF_xxx */
	char	*dom_name;
	void	(*dom_init)		/* initialize domain data structures */
		(void);
	int	(*dom_externalize)	/* externalize access rights */
		(struct mbuf *, struct mbuf **);
	void	(*dom_dispose)		/* dispose of internalized rights */
		(struct mbuf *);
	struct	protosw *dom_protosw, *dom_protoswNPROTOSW;
	struct	domain *dom_next;
	int	(*dom_rtattach)		/* initialize routing table */
		(void **, int);
	int	dom_rtoffset;		/* an arg to rtattach, in bits */
	int	dom_maxrtkey;		/* for routing layer */
};
.Ed
.Pp
Each domain contains an array of protocol switch structures
.Pq Vt "struct protosw *" ,
one for each socket type supported.
.Bd -literal
struct protosw {
	short	pr_type;		/* socket type used for */
	struct	domain *pr_domain;	/* domain protocol a member of */
	short	pr_protocol;		/* protocol number */
	short	pr_flags;		/* see below */
/* protocol-protocol hooks */
	pr_input_t *pr_input;		/* input to protocol (from below) */
	pr_output_t *pr_output;		/* output to protocol (from above) */
	pr_ctlinput_t *pr_ctlinput;	/* control input (from below) */
	pr_ctloutput_t *pr_ctloutput;	/* control output (from above) */
/* user-protocol hook */
	pr_usrreq_t	*pr_ousrreq;
/* utility hooks */
	pr_init_t *pr_init;
	pr_fasttimo_t *pr_fasttimo;	/* fast timeout (200ms) */
	pr_slowtimo_t *pr_slowtimo;	/* slow timeout (500ms) */
	pr_drain_t *pr_drain;		/* flush any excess space possible */

	struct	pr_usrreqs *pr_usrreqs;	/* supersedes pr_usrreq() */
	struct	pfil_head	pr_pfh;
};
.Ed
.Pp
The following functions handle the registration of a new domain,
lookups of specific protocols and protocol types within those domains,
and handle control messages from the system.
.Pp
.Fn pfctlinput
is called by the system whenever an event occurs that could affect every
domain.
Examples of those types of events are routing table changes, interface
shutdowns or certain
.Tn ICMP
message types.
When called,
.Fn pfctlinput
calls the protocol specific
.Fn pr_ctlinput
function for each protocol in that has defined one, in every domain.
.Pp
.Fn pfctlinput2
provides that same functionality of
.Fn pfctlinput ,
but with a few additional checks and a new
.Vt "void *"
argument that is passed directly to the protocol's
.Fn pr_ctlinput
function.
Unlike
.Fn pfctlinput ,
.Fn pfctlinput2
verifies that
.Fa sa
is not
.Dv NULL ,
and that only the protocol families that are the same as
.Fa sa
have their
.Fn pr_ctlinput
function called.
.Pp
.Fn net_add_domain
adds a new protocol domain to the system.
The argument
.Fa data
is cast directly to
.Vt "struct domain *"
within the function, but is declared
.Vt "void *"
in order to prevent compiler warnings when new domains are registered with
.Fn SYSINIT .
In most cases
.Fn net_add_domain
is not called directly, instead
.Fn DOMAIN_SET
is used.
.Pp
If the new domain has defined an initialization routine, it is called by
.Fn net_add_domain ;
as well, each of the protocols within the domain that have defined an
initialization routine will have theirs called.
.Pp
Once a domain is added it cannot be unloaded.
This is because there is
no reference counting system in place to determine if there are any
active references from sockets within that domain.
.Pp
.Fn pffindtype
and
.Fn pffindproto
look up a protocol by its number or by its type.
In most cases, if the protocol or type cannot be found,
.Dv NULL
is returned, but
.Fn pffindproto
may return the default if the requested type is
.Dv SOCK_RAW ,
a protocol switch type of
.Dv SOCK_RAW
is found, and the domain has a default raw protocol.
.Pp
Both functions are called by
.Fn socreate
in order to resolve the protocol for the socket currently being created.
.Pp
.Fn DOMAIN_SET
is a macro that simplifies the registration of a domain via
.Fn SYSINIT .
The code resulting from the macro expects there to be a domain structure
named
.Dq Fa name Ns Li domain
where
.Fa name
is the argument to
.Fn DOMAIN_SET :
.Bd -literal
struct domain localdomain =
{ AF_LOCAL, "local", unp_init, unp_externalize, unp_dispose,
  localsw, &localsw[sizeof(localsw)/sizeof(localsw[0])] };

DOMAIN_SET(local);
.Ed
.Sh RETURN VALUES
Both
.Fn pffindtype
and
.Fn pffindproto
return a
.Vt "struct protosw *"
for the protocol requested.
If the protocol or socket type is not found,
.Dv NULL
is returned.
In the case of
.Fn pffindproto ,
the default protocol may be returned for
.Dv SOCK_RAW
types if the domain has a default raw protocol.
.Sh SEE ALSO
.Xr socket 2
.Sh AUTHORS
This manual page was written by
.An Chad David Aq davidc@acns.ab.ca .