NAME

       seccomp_init, seccomp_reset - Initialize the seccomp filter state

SYNOPSIS

       #include <seccomp.h>

       typedef void * scmp_filter_ctx;

       scmp_filter_ctx seccomp_init(uint32_t def_action);
       int seccomp_reset(scmp_filter_ctx ctx, uint32_t def_action);

       Link with -lseccomp.

DESCRIPTION

       The  seccomp_init()  and  seccomp_reset()  functions  (re)initialize  the  internal seccomp filter state,
       prepares it for use, and sets the default action based on the def_action parameter.   The  seccomp_init()
       function must be called before any other libseccomp functions as the rest of the library API will fail if
       the filter context is not initialized properly.   The  seccomp_reset()  function  releases  the  existing
       filter  context  state before reinitializing it and can only be called after a call to seccomp_init() has
       succeeded.  If seccomp_reset() is called with a NULL filter, it resets the library's global  task  state,
       including  any  notification  file  descriptors  retrieved by seccomp_notify_fd(3).  Normally this is not
       needed, but it may be required to continue using the library after a fork() or clone() call to ensure the
       API level and user notification state is properly reset.

       When  the caller is finished configuring the seccomp filter and has loaded it into the kernel, the caller
       should call seccomp_release(3) to release all of the filter context state.

       Valid def_action values are as follows:

       SCMP_ACT_KILL
              The thread will be terminated by the kernel with SIGSYS when it calls  a  syscall  that  does  not
              match  any  of  the  configured  seccomp  filter  rules.  The thread will not be able to catch the
              signal.

       SCMP_ACT_KILL_PROCESS
              The entire process will be terminated by the kernel with SIGSYS when it calls a syscall that  does
              not match any of the configured seccomp filter rules.

       SCMP_ACT_TRAP
              The  thread  will  be  sent a SIGSYS signal when it calls a syscall that does not match any of the
              configured seccomp filter rules.  It may catch this and change  its  behavior  accordingly.   When
              using  SA_SIGINFO with sigaction(2), si_code will be set to SYS_SECCOMP, si_syscall will be set to
              the syscall that failed the rules, and si_arch will be set to the AUDIT_ARCH for the active ABI.

       SCMP_ACT_ERRNO(uint16_t errno)
              The thread will receive a return value of errno when it calls a syscall that does not match any of
              the configured seccomp filter rules.

       SCMP_ACT_TRACE(uint16_t msg_num)
              If  the  thread is being traced and the tracing process specified the PTRACE_O_TRACESECCOMP option
              in the call to ptrace(2), the tracing process will be notified, via PTRACE_EVENT_SECCOMP, and  the
              value provided in msg_num can be retrieved using the PTRACE_GETEVENTMSG option.

       SCMP_ACT_LOG
              The  seccomp filter will have no effect on the thread calling the syscall if it does not match any
              of the configured seccomp filter rules but the syscall will be logged.

       SCMP_ACT_ALLOW
              The seccomp filter will have no effect on the thread calling the syscall if it does not match  any
              of the configured seccomp filter rules.

RETURN VALUE

       The  seccomp_init()  function  returns a filter context on success, NULL on failure.  The seccomp_reset()
       function returns zero on success or one of the following error codes on failure:

       -EINVAL
              Invalid input, either the context or action is invalid.

       -ENOMEM
              The library was unable to allocate enough memory.

EXAMPLES

       #include <seccomp.h>

       int main(int argc, char *argv[])
       {
            int rc = -1;
            scmp_filter_ctx ctx;

            ctx = seccomp_init(SCMP_ACT_KILL);
            if (ctx == NULL)
                 goto out;

            /* ... */

            rc = seccomp_reset(ctx, SCMP_ACT_KILL);
            if (rc < 0)
                 goto out;

            /* ... */

       out:
            seccomp_release(ctx);
            return -rc;
       }

NOTES

       While the seccomp filter can be generated independent of the kernel, kernel support is required  to  load
       and enforce the seccomp filter generated by libseccomp.

       The  libseccomp  project  site,  with  more  information  and the source code repository, can be found at
       https://github.com/seccomp/libseccomp.  This tool, as well as the libseccomp library, is currently  under
       development, please report any bugs at the project site or directly to the author.

AUTHOR

       Paul Moore <paul@paul-moore.com>

SEE ALSO

       seccomp_release(3)