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OpenDarwin 7.2.1 - man page for ipsec_set_policy (opendarwin section 3)

IPSEC_SET_POLICY(3)		   BSD Library Functions Manual 	      IPSEC_SET_POLICY(3)

     ipsec_set_policy, ipsec_get_policylen, ipsec_dump_policy -- manipulate IPsec policy specifi-
     cation structure from readable string

     IPsec Policy Control Library (libipsec, -lipsec)

     #include <netinet6/ipsec.h>

     char *
     ipsec_set_policy(char *policy, int len);

     ipsec_get_policylen(char *buf);

     char *
     ipsec_dump_policy(char *buf, char *delim);

     ipsec_set_policy() generates IPsec policy specification structure, namely struct
     sadb_x_policy and/or struct sadb_x_ipsecrequest from human-readable policy specification.
     Policy specification must be given as C string policy and length len of policy.
     ipsec_set_policy() will return the buffer of IPsec policy specification structure.

     You may want the length of the generated buffer such when calling setsockopt(2).
     ipsec_get_policylen() will return the length.

     ipsec_dump_policy() converts IPsec policy structure into readable form.  Therefore,
     ipsec_dump_policy() can be regarded as inverse conversion of ipsec_set_policy().  buf points
     to a IPsec policy structure, struct sadb_x_policy.  delim is a delimiter string, which is
     usually a blank character.  If you set delim to NULL, single whitespace is assumed.
     ipsec_dump_policy() returns pointer to dynamically allocated string.  It is caller's respon-
     sibility to reclaim the region, by using free(3).

     policy is formatted as either of the following:

     direction discard
	      direction must be in or out.  direction specifies which direction the policy needs
	      to be applied.  With discard policy, packets will be dropped if they match the pol-

     direction entrust
	      entrust means to consult to SPD defined by setkey(8).

     direction bypass
	      bypass means to be bypassed the IPsec processing.  (packet will be transmitted in
	      clear).  This is for privileged socket.

     direction ipsec request ...
	      ipsec means that the matching packets are subject to IPsec processing.  ipsec can
	      be followed by one or more request string, which is formatted as below:

	      protocol / mode / src - dst [/level]
		       protocol is either ah, esp or ipcomp.

		       mode is either transport or tunnel.

		       src and dst specifies IPsec endpoint.  src always means ``sending node''
		       and dst always means ``receiving node''.  Therefore, when direction is in,
		       dst is this node and src is the other node (peer).  If mode is transport,
		       Both src and dst can be omited.

		       level must be set to one of the following: default, use, require or
		       unique.	default means that the kernel should consult the system default
		       policy defined by sysctl(8), such as net.inet.ipsec.esp_trans_deflev.  See
		       ipsec(4) regarding the system default.  use means that a relevant SA can
		       be used when available, since the kernel may perform IPsec operation
		       against packets when possible.  In this case, packets can be transmitted
		       in clear (when SA is not available), or encrypted (when SA is available).
		       require means that a relevant SA is required, since the kernel must per-
		       form IPsec operation against packets.  unique is the same as require, but
		       adds the restriction that the SA for outbound traffic is used only for
		       this policy.  You may need the identifier in order to relate the policy
		       and the SA when you define the SA by manual keying.  You can put the deci-
		       mal number as the identifier after unique like unique: number.  number
		       must be between 1 and 32767 .  If the request string is kept unambiguous,
		       level and slash prior to level can be omitted.  However, it is encouraged
		       to specify them explicitly to avoid unintended behaviors.  If level is
		       omitted, it will be interpreted as default.

     Note that there is a bit difference of specification from setkey(8).  In specification by
     setkey(8), both entrust and bypass are not used.  Refer to setkey(8) for detail.

     Here are several examples (long lines are wrapped for readability):

	   in discard
	   out ipsec esp/transport//require
	   in ipsec ah/transport//require
	   out ipsec esp/tunnel/
	   in ipsec ipcomp/transport//use

     ipsec_set_policy() returns a pointer to the allocated buffer of policy specification if suc-
     cessful; otherwise a NULL pointer is returned.  ipsec_get_policylen() returns with positive
     value (meaning the buffer size) on success, and negative value on errors.
     ipsec_dump_policy() returns a pointer to dynamically allocated region on success, and NULL
     on errors.

     ipsec_strerror(3), ipsec(4), setkey(8)

     The functions first appeared in WIDE/KAME IPv6 protocol stack kit.

     IPv6 and IPsec support based on the KAME Project (http://www.kame.net/) stack was initially
     integrated into FreeBSD 4.0

BSD					   May 5, 1998					      BSD

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