parser.h

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/**
 * @file parser.h
 * @brief Function prototypes for @p parser.y, config-related magic numbers and
 *        data structures
 * @note @p parser.y is not documented with Doxygen.
 */
#pragma once

#include <stdint.h>
#include <net/if.h>
#include <linux/if_ether.h>

/**
 * @name Magic number definitions
 * @{
 */
#define IFACE_SET_MAC                   0xff
#define TCI_NO_DOT1Q                    0xef
#define TCI_UNTOUCHED                   0xff
#define TCI_UNTOUCHED_16                0xffff
/** @} */

/**
 * @brief 802.1Q VLAN Tag Control Information
 *
 * Stores the three variable fields in a 4-byte 802.1Q VLAN tag.
 */
struct tci_t {
        uint8_t pcp;                    /**< @brief Priority Code Point */
        uint8_t dei;                    /**< @brief Drop Eligible Indicator */
        uint16_t vid;                   /**< @brief Identifier */
};

/**
 * @brief Bitmasks for filtering on EAPOL Packet Type or EAP Code.
 *
 * The respective ranges of EAPOL Packet Types and EAP Codes are 0-8 (requires 2
 * bytes) and 1-4.
 * @note Whether an instance of <tt>struct filter_t</tt> stores ingress or
 * egress filters depends on whether its parent is a <tt>struct ingress_t</tt>
 * or a <tt>struct egress_t</tt>.
 */
struct filter_t {
        uint16_t type;                  /**< @brief Filter on EAPOL Packet Type */
        uint8_t code;                   /**< @brief Filter on EAP Code */
};

/**
 * @brief Scripts to execute on EAPOL Packet Type or EAP Code
 *
 * @p type and @p code are arrays of C strings. Each element contains either the
 * path to an executable script or @p NULL.
 *
 * @note Whether an instance of <tt>struct filter_t</tt> stores ingress or
 * egress scripts depends on whether its parent is a <tt>struct ingress_t</tt>
 * or a <tt>struct egress_t</tt>.
 * @note EAP Codes only range from 1-4, so @p packet[0] is always @p NULL.
 */
struct action_t {
        char *type[9];                  /**< @brief Run script on EAPOL Packet Type */
        char *code[5];                  /**< @brief Run script on EAP Code */
};

/** @brief Behavior during the ingress phase for an interface */
struct ingress_t {
        struct action_t *action;        /**< @brief Run script on ingress */
        struct filter_t *filter;        /**< @brief Filter on ingress */
};

/** @brief Behavior during the egress phase for an interface */
struct egress_t {
        struct tci_t *tci;              /**< @brief Add/edit/remove VLAN tag on egress */
        struct filter_t *filter;        /**< @brief Filter on egress */
        struct action_t *action;        /**< @brief Run script on egress */
};

/**
 * @brief Represents a network interface and its associated config
 *
 * Also a node in a singly linked list of <tt>struct iface_t</tt> structures.
 */
struct iface_t {
        char name[IFNAMSIZ];            /**< @brief Network interface name. */
        unsigned index;                 /**< @brief Interface index */
        int mtu;                        /**< @brief Maximum Transmission Unit */
        int skt;                        /**< @brief Raw socket bound to the interface */
        unsigned recv_ctr;              /**< @brief Number of EAPOL packets received */
        unsigned send_ctr;              /**< @brief Number of EAPOL packets sent */
        struct ingress_t *ingress;      /**< @brief Ingress options */
        struct egress_t *egress;        /**< @brief Egress options */
        uint8_t promisc;                /**< @brief Flag: Set promiscuous mode on @p skt? */
        /**
         * @brief A MAC address, plus a magic number
         *
         * During program startup, the current interface's MAC address will be
         * changed to match the first @p ETH_ALEN bytes of this field, and the
         * final byte of this field will be cleared.
         *
         * @note If this is set by the parser, its final byte will be set to
         *       <tt>IFACE_SET_MAC</tt>, and the @p set_mac_from field will not
         *       be set.
         */
        u_char set_mac[ETH_ALEN + 1];
        /**
         * @brief Index of another configured interface
         *
         * When that interface receives an EAPOL packet for the first time,
         * the current interface's MAC address will be changed to match the
         * packet's source MAC address, and this field will be cleared.
         *
         * @note If this is set by the parser, the @p set_mac field will not
         *       be set.
         */
        unsigned set_mac_from;
        struct iface_t *next;           /**< @brief Next node */
};

struct iface_t *parse_config(const char *path, uint8_t *level);
void parser_print_ifaces(struct iface_t *list);