DOMAIN(9)

NAME
domain_add, domain_init, pfctlinput, pffinddomain, pffindproto, pffindtype, DOMAIN_SET - network domain management

SYNOPSIS
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/protosw.h>
#include <sys/domain.h>
void
domain_add(void *data);
void
domain_init(void *data);
void
pfctlinput(int cmd, struct sockaddr *sa);
struct domain *
pffinddomain(int family);
struct protosw *
pffindproto(int family, int protocol, int type);
struct protosw *
pffindtype(int family, int type);
void
DOMAIN_SET(name);

DESCRIPTION
Network protocols installed in the system are maintained within what are called domains (for example the inetdomain and localdomain).

    struct domain {
    	int	dom_family;		/* AF_xxx */
    	char	*dom_name;
    	int	dom_flags;
    	int	(*dom_probe)(void);	/* check for support (optional) */
    	void	(*dom_destroy)		/* cleanup structures / state */
    		(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_rtdetach)		/* clean up routing table */
    		(void **, int);
    	void	*(*dom_ifattach)(struct ifnet *);
    	void	(*dom_ifdetach)(struct ifnet *, void *);
    	int	(*dom_ifmtu)(struct ifnet *);
    					/* af-dependent data on ifnet */
    };

Each domain contains an array of protocol switch structures (struct protosw *), one for each socket type supported.

    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) */
    /* utility hooks */
    	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;	/* user-protocol hook */
    };

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.

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 ICMP message types. When called, pfctlinput() calls the protocol specific pr_ctlinput() function for each protocol in that has defined one, in every domain.

domain_add() adds a new protocol domain to the system. The argument data is cast directly to struct domain * within the function, but is declared void * in order to prevent compiler warnings when new domains are registered with SYSINIT(). In most cases domain_add() is not called directly, instead DOMAIN_SET() is used.

If the new domain has defined a probe routine, it is called first in domain_add() to determine if the domain should be supported on the current system. If the probe routine returns a non-0 value, then the domain will not be marked as supported. Unsupported domains do not proceed with the initialization process and are not discoverable by pffinddomain(), pffindtype(), or pffindproto().

domain_init() is called after domain_add() during boot and for each vnet(9). If the new domain has defined an initialization routine, it is called during domain_init(); as well, each of the protocols within the domain that have defined an initialization routine will have theirs called. Note that domain initialization cannot fail at this time.

Once a domain is added it cannot be completely 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. If the domain defines a dom_destroy() routine, then it will be invoked during vnet teardown.

pffinddomain() finds a domain by family. If the domain cannot be found, NULL is returned.

pffindtype() and pffindproto() look up a protocol by its number or by its type. In most cases, if the protocol or type cannot be found, NULL is returned, but pffindproto() may return the default if the requested type is SOCK_RAW, a protocol switch type of SOCK_RAW is found, and the domain has a default raw protocol.

Both functions are called by socreate() in order to resolve the protocol for the socket currently being created.

DOMAIN_SET() is a macro that simplifies the registration of a domain via SYSINIT(). The code resulting from the macro expects there to be a domain structure named “namedomain” where name is the argument to DOMAIN_SET():

    struct domain localdomain =
    { AF_LOCAL, "local", unp_init, unp_externalize, unp_dispose,
      localsw, &localsw[sizeof(localsw)/sizeof(localsw[0])] };
    DOMAIN_SET(local);

RETURN VALUES
Both pffindtype() and pffindproto() return a struct protosw * for the protocol requested. If the protocol or socket type is not found, NULL is returned. In the case of pffindproto(), the default protocol may be returned for SOCK_RAW types if the domain has a default raw protocol.

SEE ALSO
socket(2)

HISTORY
The functions domain_add(), pfctlinput(), pffinddomain(), pffindproto(), pffindtype() and DOMAIN_SET() first appeared in FreeBSD 4.4.

AUTHORS
This manual page was written by Chad David <davidc@acns.ab.ca>.