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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 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);

     The ipsec_set_policy() function 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.  The
     ipsec_set_policy() function will return the buffer of IPsec policy
     specification structure.  The buffer is dynamically allocated, and must
     be freed by the caller by calling free(3).

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

     The ipsec_dump_policy() function converts IPsec policy structure into
     readable form.  Therefore, ipsec_dump_policy() can be regarded as inverse
     conversion of ipsec_set_policy().  buf points to an 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.  The ipsec_dump_policy() function returns a 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 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 policy.

     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 omitted.

                       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 perform
                       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 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.
                       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

     The ipsec_set_policy() function returns a pointer to the allocated buffer
     of policy specification if successful; otherwise a NULL pointer is
     returned.  The ipsec_get_policylen() function returns with positive value
     (meaning the buffer size) on success, and negative value on errors.  The
     ipsec_dump_policy() function 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 (
     stack was initially integrated into FreeBSD 4.0

FreeBSD 11.0-PRERELEASE           May 5, 1998          FreeBSD 11.0-PRERELEASE


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