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IPSEC_SET_POLICY(3)    FreeBSD Library Functions Manual    IPSEC_SET_POLICY(3)

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

     IPsec Support 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-read­
     able 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 responsibility to reclaim the region, by using free(3).

     policy is formatted as either of the following:

     direction entrust
	      direction must be in or out. direction specifies which direction
	      the policy needs to be applied.  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 pro­
	      cessing.	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).

		       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 transmit­
		       ted 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 perform IPsec op­
		       eration against packets.  unique is the same as
		       require, but adds the restriction that the SA for out­
		       bound 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 decimal 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.  Howev­
		       er, 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/
	   in ipsec ah/transport/
	   out ipsec esp/transport/
	   in ipsec ipcomp/transport/

     ipsec_set_policy() returns a pointer to the allocated buffer of policy
     specification if successful; 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() re­
     turns a pointer to dynamically allocated region on success, and NULL on

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

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

BSD				  May 5, 1998				     2


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