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LIBBLOCKLIST(3) Library Functions Manual LIBBLOCKLIST(3) NAME blocklist_open, blocklist_open2, blocklist_close, blocklist_r, blocklist, blocklist_sa, blocklist_sa_r -- Blocklistd notification li- brary LIBRARY library "libblocklist" SYNOPSIS #include <blocklist.h> struct blocklist * blocklist_open(void); struct blocklist * blocklist_open2(void (*logger)(int, struct syslog_data *, va_list)); void blocklist_close(struct blocklist *cookie); int blocklist(int action, int fd, const char *msg); int blocklist_r(struct blocklist *cookie, int action, int fd, const char *msg); int blocklist_sa(int action, int fd, const struct sockaddr *sa, socklen_t salen, const char *msg); int blocklist_sa_r(struct blocklist *cookie, int action, int fd, const struct sockaddr *sa, socklen_t salen, const char *msg); DESCRIPTION These functions can be used by daemons to notify blocklistd(8) about successful and failed remote connections so that blocklistd can block or release port access to prevent Denial of Service attacks. The function blocklist_open() creates the necessary state to communi- cate with blocklistd(8) and returns a pointer to it, or NULL on fail- ure. The function blocklist_open2() is similar to blocklist_open() but al- lows a logger to be specified. If the logger is NULL, then no logging is performed. The blocklist_close() function frees all memory and resources used. The blocklist() function sends a message to blocklistd(8), with an in- teger action argument specifying the type of notification, a file de- scriptor fd specifying the accepted file descriptor connected to the client, and an optional message in the msg argument. The action parameter can take these values: BLOCKLIST_AUTH_FAIL There was an unsuccessful authentication attempt. BLOCKLIST_AUTH_OK A user successfully authenticated. BLOCKLIST_ABUSIVE_BEHAVIOR The sending daemon has detected abusive be- havior from the remote system. The remote address should be blocked as soon as possi- ble. BLOCKLIST_BAD_USER The sending daemon has determined the user- name presented for authentication is in- valid. The blocklistd(8) daemon compares the username to a configured list of for- bidden usernames and blocks the address im- mediately if a forbidden username matches. (The BLOCKLIST_BAD_USER support is not cur- rently available.) The blocklist_r() function is more efficient because it keeps the blocklist state around. The blocklist_sa() and blocklist_sa_r() functions can be used with un- connected sockets, where getpeername(2) will not work, the server will pass the peer name in the message. In all cases the file descriptor passed in the fd argument must be pointing to a valid socket so that blocklistd(8) can establish owner- ship of the local endpoint using getsockname(2). By default, syslogd(8) is used for message logging. The internal bl_create() function can be used to create the required internal state and specify a custom logging function. RETURN VALUES The function blocklist_open() returns a cookie on success and NULL on failure setting errno to an appropriate value. The functions blocklist(), blocklist_sa(), and blocklist_sa_r() return 0 on success and -1 on failure setting errno to an appropriate value. SEE ALSO blocklistd.conf(5), blocklistd(8) AUTHORS Christos Zoulas FreeBSD 15.0 February 5, 2025 LIBBLOCKLIST(3)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | AUTHORS
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