libinn(3)

NAME
libinn - InterNetNews library routines

SYNOPSIS
    #include "inn/libinn.h"

    #define ISWHITE(c) ...

    /* Headers-related routines. */
    extern char *GenerateMessageID(char *domain);
    extern void HeaderCleanFrom(char *from);
    extern struct _DDHANDLE *DDstart(FILE *FromServer, FILE *ToServer);
    extern void DDcheck(struct _DDHANDLE *h, char *group);
    extern char *DDend(struct _DDHANDLE *h);

    /* Cancel-Lock routines. */
    extern bool gen_cancel_lock(const char *msgid, const char *username,
                                char **canbuff);
    extern bool gen_cancel_key(const char *hdrcontrol,
                               const char *hdrsupersedes,
                               const char *username, char **canbuff);
    extern bool verify_cancel_key(const char *c_key_header,
                                  const char *c_lock_header);

    /* Opening the active file on a client. */
    extern FILE *CAopen(FILE *FromServer, FILE *ToServer);
    extern FILE *CAlistopen(FILE *FromServer, FILE *ToServer,
                            const char *request);
    extern void CAclose(void);

    /* File locking. */
    enum inn_locktype
    {
        INN_LOCK_READ,
        INN_LOCK_WRITE,
        INN_LOCK_UNLOCK
    };

    extern bool inn_lock_file(int fd, enum inn_locktype type,
                              bool block);

    /* NNTP functions. */
    extern int NNTPlocalopen(FILE **FromServerp, FILE **ToServerp,
                             char *errbuff, size_t len);
    extern int NNTPremoteopen(int port, FILE **FromServerp,
                              FILE **ToServerp, char *errbuff,
                              size_t len);
    extern int NNTPconnect(const char *host, int port,
                           FILE **FromServerp, FILE **ToServerp,
                           char *errbuff, size_t len);
    extern int NNTPsendarticle(char *text, FILE *ToServer,
                               bool terminate);
    extern int NNTPsendpassword(char *server, FILE *FromServer,
                                FILE *ToServer);

    /* Hash functions. */
    typedef struct {
        char hash[16];
    } HASH;

    extern HASH HashMessageID(const char *MessageID);

    /* Other useful functions. */
    extern char *inn_getfqdn(const char *domain);
    extern char *GetModeratorAddress(FILE *FromServer, FILE *ToServer,
                                     char *group, char *moderatormailer);

    /* Miscellaneous. */
    extern int GetResourceUsage(double *usertime, double *systime);
    extern void Radix32(unsigned long value, char *buff);
    extern char *ReadInDescriptor(int fd, struct stat *Sbp);
    extern char *ReadInFile(const char *name, struct stat *Sbp);

    /* Reserving file descriptors. */
    extern bool fdreserve(int fdnum);
    extern FILE *Fopen(const char *name, const char *mode, int fdindex);
    extern int Fclose(FILE *fp);

    /* Determining, setting and checking the limit on open file
       descriptors. */
    extern int getfdlimit(void);
    extern int setfdlimit(unsigned int limit);
    extern bool isvalidfd(unsigned int fd);

    /* Setting or clearing file descriptor flags. */
    #include "inn/fdflag.h"

    bool fdflag_close_exec(int fd, bool flag);
    bool fdflag_nonblocking(socket_type fd, bool flag);

DESCRIPTION
libinn is a library of utility routines for manipulating Usenet articles and related data. The whole documentation of libinn routines is split into several specific man pages besides this one: libinn_clientlib(3), libinn_dbz(3), libinn_inndcomm(3), libinn_list(3), libinn_qio(3), libinn_tst(3) and libinn_uwildmat(3).

  MACROS
"ISWHITE" is a macro which tests whether its char argument is a space or a tabulation.

  HEADERS-RELATED ROUTINES
GenerateMessageID uses the current time, nnrpd's process ID, a global static counter incrementing at each post in the same NNTP session, and a fully qualified domain name, which is passed as an argument, to create a Message-ID header field that is highly likely to be unique. The returned value points to static space that is reused on subsequent calls. If the argument is NULL, inn_getfqdn is called to find a suitable FQDN (using domain as set in inn.conf to qualify the local host name if local host cannot be resolved in DNS).

HeaderCleanFrom removes the extraneous information from the value of a From or Reply-To header field and leaves just the official mailing address. In particular, the following transformations are made to the from parameter:

•   address --> address

•   address (stuff) --> address

•   stuff <address> --> address

The transformations are simple, based on RFC 5536 which limits the format of the header field.

DDstart, DDcheck, and DDend are used to set the Distribution header field; the "DD" stands for Default Distribution. The distrib.pats file is consulted to determine the proper value for the Distribution header field after all newsgroups have been checked. DDstart begins the parsing. It returns a pointer to an opaque handle that should be used on subsequent calls. The FromServer and ToServer parameters should be "FILE"'s connected to the NNTP server for input and output, respectively. If either parameter is NULL, then an empty default will ultimately be returned if the file is not locally available.

DDcheck should be called with the handle, h, returned by DDstart and a newsgroup, group, to check. It can be called as often as necessary.

DDend releases any state maintained in the handle and returns an allocated copy of the text that should be used for the Distribution header field.

  CANCEL-LOCK
These routines are available in libinn if INN was built with Cancel-Lock support (otherwise they are stub functions which are always returning false). The "configure" script automatically enables that support if it finds libcanlock.

gen_cancel_lock expects a Message-ID, a username (possibly NULL) and the address of a pointer where it will write elements suitable for the body of a Cancel-Lock header field.

gen_cancel_key expects a Control header field body (possibly NULL), a Supersedes header field body (possibly NULL), a username (possibly NULL) and the address of a pointer where it will write elements suitable for the body of a Cancel-Key header field. This function extracts the Message-ID from the Control header field body or, if NULL, from the Supersedes header field body. If the header field used for that extraction is not correctly formatted, or they are both NULL, or no Message-ID is found, it will result in a failure.

These functions return true if all the elements were written, false on failure. The canbuff string will be allocated by these functions, unless they return false. The caller is responsible for freeing it.

For each admin secret in the canlockadmin vector set in inn.conf, and for each user secret set in the canlockuser vector set in inn.conf if username is not NULL, gen_cancel_lock will generate in canbuff both sha1 and sha256 Base64-encoded hashes. Regarding gen_cancel_key, it will be for each admin secret in the canlockadmin vector if username is NULL or for each user secret in the canlockuser vector if username is not NULL.

verify_cancel_lock expects pointers to Cancel-Key and Cancel-Lock header field bodies. This function verifies that c_key_header contains an element matching one of those present in c_lock_header. It returns true if at least one element matches. Otherwise, false is returned, that is to say the cancel or supersede request cannot be authenticated.

  CLIENT ACTIVE FILE
CAopen and CAclose provide news clients with access to the active file; the "CA" stands for Client Active. CAopen opens the active file for reading. It returns a pointer to an open "FILE", or NULL on error. If a local or NFS-mounted copy exists, CAopen will use that file. The FromServer and ToServer parameters should be "FILE"'s connected to the NNTP server for input and output, respectively. See NNTPremoteopen or NNTPlocalopen, below. If either parameter is NULL, then CAopen will just return NULL if the file is not locally available. If they are not NULL, CAopen will use them to query the NNTP server using the LIST command to make a local temporary copy.

The CAlistopen sends a LIST command to the server and returns a temporary file containing the results. The request parameter, if not NULL, will be sent as an argument to the command. Unlike CAopen, this routine will never use a locally-available copy of the active file.

CAclose closes the active file and removes any temporary file that might have been created by CAopen or CAlistopen.

  FILE LOCKING
inn_lock_file tries to lock the file descriptor fd. If block is true, it will block until the lock can be made, otherwise it will return false if the file cannot be locked. type is one of "INN_LOCK_READ", "INN_LOCK_WRITE" or "INN_LOCK_UNLOCK". It returns false on failure or true on success.

  NNTP FUNCTIONS
NNTPlocalopen opens a connection to the private port of an InterNetNews server running on the local host, if "HAVE_UNIX_DOMAIN_SOCKETS" in include/config.h is defined. It returns "-1" on failure, or "0" on success. FromServerp and ToServerp will be filled in with "FILE"'s which can be used to communicate with the server. errbuff can either be NULL or a pointer to a buffer at least 512 bytes long. If not NULL, and the server refuses the connection, then it will be filled in with the text of the server's reply. len should be the length of the errbuff buffer. This routine is not for general use. If "HAVE_UNIX_DOMAIN_SOCKETS" in include/config.h is not defined, this is a stub routine, for compatibility with systems that have Unix-domain stream sockets, and it then always returns "-1".

NNTPremoteopen does the same, except that it uses the server parameter set in inn.conf as the local server, and opens a connection to the port. Any client program can use this routine. It returns "-1" on failure, or "0" on success.

NNTPconnect is the same as NNTPremoteopen except that the desired host is given as the host parameter.

NNTPsendarticle writes text on ToServer using NNTP conventions for line termination. The text should consist of one or more lines ending with a newline. If terminate is true, then the routine will also write the NNTP data-termination marker on the stream. It returns "-1" on failure, or "0" on success.

NNTPsendpassword sends authentication information to an NNTP server by finding the appropriate entry in the passwd.nntp file. server contains the name of the host; the server parameter in inn.conf will be used if server is NULL. FromServer and ToServer should be "FILE"'s that are connected to the server. No action is taken if the specified host is not listed in the password file.

  HASHES
HashMessageID returns hashed Message-ID using MD5.

  OTHER USEFUL FUNCTIONS
inn_getfqdn returns the fully qualified domain name of the local host. inn_getfqdn first tries to retrieve it from the INN_HOSTNAME environment variable if set, then from gethostname(3) and getaddrinfo(3) calls. The check is very simple; if the retrieved hostname contains a period, then it is assumed to have the full domain name. Otherwise, if domain is set in inn.conf, a dot followed with the value of domain is appended to the retrieved hostname to qualify the local host name. The returned value points to newly-allocated memory that the caller is responsible for freeing, or NULL on error.

GetModeratorAddress returns the mailing address of the moderator for specified group or NULL on error. moderatormailer is used as its address, if there is no matched moderator. See moderators(5) for details on how the address is determined. GetModeratorAddress does no checking to see if the specified group is actually moderated. The returned value points to static space that is reused on subsequent calls. The FromServer and ToServer parameters should be "FILE"'s connected to the NNTP server for input and output, respectively. If either of these parameters is NULL, then an attempt to get the list from a local copy is made.

  MISCELLANEOUS
GetResourceUsage fills in the usertime and systime parameters with the total user and system time used by the current process and any children it may have spawned. If "HAVE_GETRUSAGE" in include/config.h is defined, it gets the values by doing a getrusage(2) system call; otherwise it calls times(2). It returns "-1" on failure, or "0" on success.

Radix32 converts the number in value into a radix-32 string into the buffer pointed to by buff. The number is split into five-bit pieces and each piece is converted into a character using the alphabet "0..9a..v" to represent the numbers "0..32". Only the lowest 32 bits of value are used, so buff needs only pointing to a buffer of eight bytes (seven characters and the trailing "\0").

ReadInFile reads the file named name into allocated memory, appending a terminating "\0" byte. It returns a pointer to the space, or NULL on error. If Sbp is not NULL, it is taken as the address of a place to store the results of a stat(2) call.

ReadInDescriptor performs the same function as ReadInFile except that fd refers to an already-open file.

  FILE DESCRIPTOR RESERVATION
fdreserve permits reserving fdnum file descriptors for future use. On platforms that have a stdio limitation, such as 64-bit Solaris versions prior to 11.0, all 32-bit Solaris versions and 32-bit applications running on 64-bit Solaris, low-numbered file descriptors can then be kept and re-used for stdio. Without this mechanism, some essential files like the history file may not have any file descriptor left when being reopened after a closure for some operations, and stdio would fail.

These file descriptors all read "/dev/null", until Fopen is called on them. If fdnum is "0" or negative, all reserved file descriptors are closed. Otherwise, fdnum file descriptors are reserved. If this function is called again with a higher fdnum value, it reserves more file descriptors; with a lower fdnum value, it closes the supernumerary reserved file descriptors. It returns true when all the file descriptors have been successfully reserved, and false otherwise, in which case all the reserved file descriptors are closed, even if some of them were previously in use.

Fopen opens the file name in the given mode, using the file descriptor in position fdindex in the reserved file descriptors. If fdindex is lower than the number of reserved file descriptors, Fopen uses the corresponding one. Otherwise, it just calls fopen(2) without re-using a reserved file descriptor. It returns a pointer to a FILE struct, or NULL on failure.

Fclose closes the file descriptor used for fp without keeping it, unless this file descriptor was a reserved one, in which case it is kept (and read "/dev/null"). It returns "0" on success. Any other value (like EOF) is a failure.

  FILE DESCRIPTOR LIMITS
getfdlimit returns the limit on open file descriptors. It uses the getrlimit(2) function when available. If not, it tries sysconf(2), then getdtablesize(2), then ulimit(2), then a possible hard-coded "NOFILE" constant in the sys/param.h system header, or then falls back to the POSIX-guaranteed minimum of 20.

setfdlimit sets the limit on open file descriptors to the given parameter limit. It uses the setrlimit(2) function when available. It returns "1" on success, and "-1" on failure (when setrlimit(2) is not available or limit is higher than select(2) can handle, checking against "FD_SETSIZE").

isvalidfd returns true if fd is not higher than the system supports, and false otherwise.

  FILE DESCRIPTOR FLAGS
fdflag_close_exec can make a descriptor close-on-exec so that it is not shared with any child processes. If the flag is true, the file is so marked; if false, the close-on-exec mode is cleared. It returns false on failure (or when the function is unsupported) or true on success.

fdflag_nonblocking enables (if flag is true) or disables (if flag is false) non-blocking I/O on the indicated "socket_type" (which can be a non-socket file descriptor on UNIX systems, but a "socket_type" is expected on Windows). It returns false on failure or true on success.

EXAMPLES
    #include "inn/fdflag.h"
    #include "inn/libinn.h"

    char *p;
    char frombuff[256], errbuff[256];
    FILE *F;
    FILE *ToServer;
    FILE *FromServer;
    int port = 119;

    strlcpy(frombuff, HDR(HDR__FROM), sizeof(frombuff));
    HeaderCleanFrom(frombuff);

    if ((F = CAopen(FromServer, ToServer)) == NULL)
        Fatal("Can't open active file");

    /* Don't pass the file on to our children. */
    fdflag_close_exec(fileno(F), true);

    /* Make a local copy. */
    p = ReadInDescriptor(fileno(F), (struct stat *) NULL);

    /* Close the file. */
    CAclose();

    if (NNTPremoteopen(port, &FromServer, &ToServer, errbuff,
                       sizeof(errbuff)) < 0)
        Fatal("Can't connect to server");

    if ((p = GetModeratorAddress(NULL, NULL, "comp.sources.unix",
                                 "%s@example.com")) == NULL)
        Fatal("Can't find moderator's address");

HISTORY
Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews. Rewritten into POD by Julien Elie.

SEE ALSO
active(5), inn.conf(5), libinn_clientlib(3), libinn_dbz(3), libinn_inndcomm(3), libinn_list(3), libinn_qio(3), libinn_tst(3), libinn_uwildmat(3), moderators(5), passwd.nntp(5).