路徑為:external\wpa_supplicant_8\wpa_supplicant\wpa_supplicant.c

/**
 * wpa_supplicant_add_iface - Add a new network interface
 * @global: Pointer to global data from wpa_supplicant_init()
 * @iface: Interface configuration options
 * Returns: Pointer to the created interface or %NULL on failure
 *
 * This function is used to add new network interfaces for %wpa_supplicant.
 * This can be called before wpa_supplicant_run() to add interfaces before the
 * main event loop has been started. In addition, new interfaces can be added
 * dynamically while %wpa_supplicant is already running. This could happen,
 * e.g., when a hotplug network adapter is inserted.
 */
 

struct wpa_supplicant * wpa_supplicant_add_iface(struct wpa_global *global,
                         struct wpa_interface *iface)
{
    struct wpa_supplicant *wpa_s;
    struct wpa_interface t_iface;
    struct wpa_ssid *ssid;

    if (global == NULL || iface == NULL)
        return NULL;

    wpa_s =
 
 wpa_supplicant_alloc();
    if (wpa_s == NULL)
        return NULL;

    wpa_s->global = global;

    t_iface = *iface;
    if (global->params.override_driver) {
        wpa_printf(MSG_DEBUG, "Override interface parameter: driver "
               "('%s' -> '%s')",
               iface->
 
driver, global->params.override_driver);
        t_iface.driver = global->params.override_driver;
    }
    if (global->params.override_ctrl_interface) {
        wpa_printf(MSG_DEBUG, "Override interface parameter: "
               "ctrl_interface ('%s' -> '%s')",
               iface->ctrl_interface,
               global->params.override_ctrl_interface);
        t_iface.ctrl_interface =
            global->params.override_ctrl_interface;
    }

    /*重要*/
    if (wpa_supplicant_init_iface(wpa_s, &t_iface)) {
        wpa_printf(MSG_DEBUG, "Failed to add interface %s",
               iface->ifname);
        wpa_supplicant_deinit_iface(wpa_s, 0, 0);
        return NULL;
    }

    /* 通過dbus通知外接有新的iface加入 Notify the control interfaces about new iface */
    if (wpas_notify_iface_added(wpa_s)) {
        wpa_supplicant_deinit_iface(wpa_s, 1, 0);
        return NULL;
    }

    /*通過dbus通知外界有新的無線網路加入*/
    for (ssid = wpa_s->conf->ssid; ssid; ssid = ssid->next)
        wpas_notify_network_added(wpa_s, ssid);

    /* wpa_global的ifaces變數指向一個wpa_supplicant物件,
     * 而wpa_supplicant又通過next變數將自己連結到一個單項鍊表中*/
    wpa_s->next = global->ifaces;
    global->ifaces = wpa_s;

    wpa_dbg(wpa_s, MSG_DEBUG, "Added interface %s", wpa_s->ifname);
    wpa_supplicant_set_state(wpa_s, WPA_DISCONNECTED);

    return wpa_s;
}

wpa_supplicant_add_iface函式的內容非常豐富, 包括兩個重要資料結構(wpa_supplicant和wpa_ssid)以及一個關鍵函式wpa_supplicant_init_iface.這些資料背景較多, 先來看看他們.

wpa_ssid結構體

wpa_ssid結構體用於儲存某個無線網路的配置資訊(如所支援的安全型別, 優先順序等). (external\wpa_supplicant_8\wpa_supplicant\wpa_supplicant.conf)檔案中的每一個network項都對應一個wpa_ssid物件.
路徑為:external\wpa_supplicant_8\wpa_supplicant\config_ssid.h

/**
 * struct wpa_ssid - Network configuration data
 *
 * This structure includes all the configuration variables for a network. This
 * data is included in the per-interface configuration data as an element of
 * the network list, struct wpa_config::ssid. Each network block in the
 * configuration is mapped to a struct wpa_ssid instance.
 * 
 */
struct wpa_ssid {
    /**
     * next - Next network in global list
     *
     * This pointer can be used to iterate over all networks. The head of
     * this list is stored in the ssid field of struct wpa_config.
     */
    struct wpa_ssid *next;/*所有wpa_ssid物件都儲存在一個連結串列當中, 頭指標保存於另外一個結構體wpa_config的ssid變數中*/

    /**
     * pnext - Next network in per-priority list
     *
     * This pointer can be used to iterate over all networks in the same
     * priority class. The heads of these list are stored in the pssid
     * fields of struct wpa_config.
     */
    struct wpa_ssid *pnext;/*wpa_ssid還可以按priority儲存在另一個連結串列中, 頭指標為wpa_config的ssid變數*/

    /**
     * id - Unique id for the network
     *
     * This identifier is used as a unique identifier for each network
     * block when using the control interface. Each network is allocated an
     * id when it is being created, either when reading the configuration
     * file or when a new network is added through the control interface.
     */
    int id;/*每個無線網路都有一個唯一的編號*/

    /**
     * priority - Priority group
     *
     * By default, all networks will get same priority group (0). If some
     * of the networks are more desirable, this field can be used to change
     * the order in which wpa_supplicant goes through the networks when
     * selecting a BSS. The priority groups will be iterated in decreasing
     * priority (i.e., the larger the priority value, the sooner the
     * network is matched against the scan results). Within each priority
     * group, networks will be selected based on security policy, signal
     * strength, etc.
     *
     * Please note that AP scanning with scan_ssid=1 and ap_scan=2 mode are
     * not using this priority to select the order for scanning. Instead,
     * they try the networks in the order that used in the configuration
     * file.
     */
    int priority;/*該無線網路對應的priority值, 預設為0*/

    /**
     * ssid - Service set identifier (network name)
     *
     * This is the SSID for the network. For wireless interfaces, this is
     * used to select which network will be used. If set to %NULL (or
     * ssid_len=0), any SSID can be used. For wired interfaces, this must
     * be set to %NULL. Note: SSID may contain any characters, even nul
     * (ASCII 0) and as such, this should not be assumed to be a nul
     * terminated string. ssid_len defines how many characters are valid
     * and the ssid field is not guaranteed to be nul terminated.
     */
    u8 *ssid;/*無線網路的名字*/

    /**
     * ssid_len - Length of the SSID
     */
    size_t ssid_len;/*ssid變數長度*/

    /**
     * bssid - BSSID
     *
     * If set, this network block is used only when associating with the AP
     * using the configured BSSID
     *
     * If this is a persistent P2P group (disabled == 2), this is the GO
     * Device Address.
     */
    u8 bssid[ETH_ALEN];/*用於儲存bssid[ETH_ALEN]*/

    /**
     * bssid_set - Whether BSSID is configured for this network
     */
    int bssid_set;/*該無線網路是否設定了bssid變數*/

    /**
     * psk - WPA pre-shared key (256 bits)
     */
    u8 psk[32];/*陣列長度為32, 用於儲存WPA中的Pre-Shared Key (256位)*/

    /**
     * psk_set - Whether PSK field is configured
     */
    int psk_set;/*是否設定了上面的psk引數*/

    /**
     * passphrase - WPA ASCII passphrase
     *
     * If this is set, psk will be generated using the SSID and passphrase
     * configured for the network. ASCII passphrase must be between 8 and
     * 63 characters (inclusive).
     */
    char *passphrase;/*為WPA設定ASCII字元密碼*/

    /**
     * ext_psk - PSK/passphrase name in external storage
     *
     * If this is set, PSK/passphrase will be fetched from external storage
     * when requesting association with the network.
     */
    char *ext_psk;

    /**
     * pairwise_cipher - Bitfield of allowed pairwise ciphers, WPA_CIPHER_*
     */
    int pairwise_cipher;/*用於單播資料加密的金鑰型別*/

    /**
     * group_cipher - Bitfield of allowed group ciphers, WPA_CIPHER_*
     */
    int group_cipher;/*用於陣列資料加密的金鑰型別*/

    /**
     * key_mgmt - Bitfield of allowed key management protocols
     *
     * WPA_KEY_MGMT_*
     */
    int key_mgmt;/*金鑰管理型別*/

    /**
     * bg_scan_period - Background scan period in seconds, 0 to disable, or
     * -1 to indicate no change to default driver configuration
     */
    int bg_scan_period;

    /**
     * proto - Bitfield of allowed protocols, WPA_PROTO_*
     */
    int proto;/*該無線網路支援的安全保護型別*/

    /**
     * auth_alg -  Bitfield of allowed authentication algorithms
     *
     * WPA_AUTH_ALG_*
     */
    int auth_alg;/*該無線網路支援的身份驗證型別*/

    /**
     * scan_ssid - Scan this SSID with Probe Requests
     *
     * scan_ssid can be used to scan for APs using hidden SSIDs.
     * Note: Many drivers do not support this. ap_mode=2 can be used with
     * such drivers to use hidden SSIDs.
     */
    int scan_ssid;/*是否利用probe request幀掃描此ssid對應的無線網路*/

#ifdef IEEE8021X_EAPOL
#define EAPOL_FLAG_REQUIRE_KEY_UNICAST BIT(0)
#define EAPOL_FLAG_REQUIRE_KEY_BROADCAST BIT(1)
    /**
     * eapol_flags - Bit field of IEEE 802.1X/EAPOL options (EAPOL_FLAG_*)
     */
    int eapol_flags;/*EAPOL選項*/

    /**
     * eap - EAP peer configuration for this network
     */
    struct eap_peer_config eap;/*eap peer端設定資訊*/
#endif /* IEEE8021X_EAPOL */

#define NUM_WEP_KEYS 4
#define MAX_WEP_KEY_LEN 16
    /**
     * wep_key - WEP keys
     */
    u8 wep_key[NUM_WEP_KEYS][MAX_WEP_KEY_LEN];

    /**
     * wep_key_len - WEP key lengths
     */
    size_t wep_key_len[NUM_WEP_KEYS];

    /**
     * wep_tx_keyidx - Default key index for TX frames using WEP
     */
    int wep_tx_keyidx;

    /**
     * proactive_key_caching - Enable proactive key caching
     *
     * This field can be used to enable proactive key caching which is also
     * known as opportunistic PMKSA caching for WPA2. This is disabled (0)
     * by default unless default value is changed with the global okc=1
     * parameter. Enable by setting this to 1.
     *
     * Proactive key caching is used to make supplicant assume that the APs
     * are using the same PMK and generate PMKSA cache entries without
     * doing RSN pre-authentication. This requires support from the AP side
     * and is normally used with wireless switches that co-locate the
     * authenticator.
     *
     * Internally, special value -1 is used to indicate that the parameter
     * was not specified in the configuration (i.e., default behavior is
     * followed).
     */
    int proactive_key_caching;

    /**
     * mixed_cell - Whether mixed cells are allowed
     *
     * This option can be used to configure whether so called mixed cells,
     * i.e., networks that use both plaintext and encryption in the same
     * SSID, are allowed. This is disabled (0) by default. Enable by
     * setting this to 1.
     */
    int mixed_cell;

#ifdef IEEE8021X_EAPOL

    /**
     * leap - Number of EAP methods using LEAP
     *
     * This field should be set to 1 if LEAP is enabled. This is used to
     * select IEEE 802.11 authentication algorithm.
     */
    int leap;

    /**
     * non_leap - Number of EAP methods not using LEAP
     *
     * This field should be set to >0 if any EAP method other than LEAP is
     * enabled. This is used to select IEEE 802.11 authentication
     * algorithm.
     */
    int non_leap;

    /**
     * eap_workaround - EAP workarounds enabled
     *
     * wpa_supplicant supports number of "EAP workarounds" to work around
     * interoperability issues with incorrectly behaving authentication
     * servers. This is recommended to be enabled by default because some
     * of the issues are present in large number of authentication servers.
     *
     * Strict EAP conformance mode can be configured by disabling
     * workarounds with eap_workaround = 0.
     */
    unsigned int eap_workaround;

#endif /* IEEE8021X_EAPOL */

    /**
     * mode - IEEE 802.11 operation mode (Infrastucture/IBSS)
     *
     * 0 = infrastructure (Managed) mode, i.e., associate with an AP.
     *
     * 1 = IBSS (ad-hoc, peer-to-peer)
     *
     * 2 = AP (access point)
     *
     * 3 = P2P Group Owner (can be set in the configuration file)
     *
     * 4 = P2P Group Formation (used internally; not in configuration
     * files)
     *
     * Note: IBSS can only be used with key_mgmt NONE (plaintext and
     * static WEP) and key_mgmt=WPA-NONE (fixed group key TKIP/CCMP). In
     * addition, ap_scan has to be set to 2 for IBSS. WPA-None requires
     * following network block options: proto=WPA, key_mgmt=WPA-NONE,
     * pairwise=NONE, group=TKIP (or CCMP, but not both), and psk must also
     * be set (either directly or using ASCII passphrase).
     */
    enum wpas_mode {
        WPAS_MODE_INFRA = 0,
        WPAS_MODE_IBSS = 1,
        WPAS_MODE_AP = 2,
        WPAS_MODE_P2P_GO = 3,
        WPAS_MODE_P2P_GROUP_FORMATION = 4,
    } mode;

    /**
     * disabled - Whether this network is currently disabled
     *
     * 0 = this network can be used (default).
     * 1 = this network block is disabled (can be enabled through
     * ctrl_iface, e.g., with wpa_cli or wpa_gui).
     * 2 = this network block includes parameters for a persistent P2P
     * group (can be used with P2P ctrl_iface commands)
     */
    int disabled;

    /**
     * disabled_for_connect - Whether this network was temporarily disabled
     *
     * This flag is used to reenable all the temporarily disabled networks
     * after either the success or failure of a WPS connection.
     */
    int disabled_for_connect;

    /**
     * peerkey -  Whether PeerKey handshake for direct links is allowed
     *
     * This is only used when both RSN/WPA2 and IEEE 802.11e (QoS) are
     * enabled.
     *
     * 0 = disabled (default)
     * 1 = enabled
     */
    int peerkey;

    /**
     * id_str - Network identifier string for external scripts
     *
     * This value is passed to external ctrl_iface monitors in
     * WPA_EVENT_CONNECTED event and wpa_cli sets this as WPA_ID_STR
     * environment variable for action scripts.
     */
    char *id_str;

#ifdef CONFIG_IEEE80211W
    /**
     * ieee80211w - Whether management frame protection is enabled
     *
     * This value is used to configure policy for management frame
     * protection (IEEE 802.11w). 0 = disabled, 1 = optional, 2 = required.
     * This is disabled by default unless the default value has been changed
     * with the global pmf=1/2 parameter.
     *
     * Internally, special value 3 is used to indicate that the parameter
     * was not specified in the configuration (i.e., default behavior is
     * followed).
     */
    enum mfp_options ieee80211w;
#endif /* CONFIG_IEEE80211W */

    /**
     * frequency - Channel frequency in megahertz (MHz) for IBSS
     *
     * This value is used to configure the initial channel for IBSS (adhoc)
     * networks, e.g., 2412 = IEEE 802.11b/g channel 1. It is ignored in
     * the infrastructure mode. In addition, this value is only used by the
     * station that creates the IBSS. If an IBSS network with the
     * configured SSID is already present, the frequency of the network
     * will be used instead of this configured value.
     */
    int frequency;

    int ht40;

    /**
     * wpa_ptk_rekey - Maximum lifetime for PTK in seconds
     *
     * This value can be used to enforce rekeying of PTK to mitigate some
     * attacks against TKIP deficiencies.
     */
    int wpa_ptk_rekey;

    /**
     * scan_freq - Array of frequencies to scan or %NULL for all
     *
     * This is an optional zero-terminated array of frequencies in
     * megahertz (MHz) to include in scan requests when searching for this
     * network. This can be used to speed up scanning when the network is
     * known to not use all possible channels.
     */
    int *scan_freq;

    /**
     * bgscan - Background scan and roaming parameters or %NULL if none
     *
     * This is an optional set of parameters for background scanning and
     * roaming within a network (ESS) in following format:
     * <bgscan module name>:<module parameters>
     */
    char *bgscan;

    /**
     * ignore_broadcast_ssid - Hide SSID in AP mode
     *
     * Send empty SSID in beacons and ignore probe request frames that do
     * not specify full SSID, i.e., require stations to know SSID.
     * default: disabled (0)
     * 1 = send empty (length=0) SSID in beacon and ignore probe request
     * for broadcast SSID
     * 2 = clear SSID (ASCII 0), but keep the original length (this may be
     * required with some clients that do not support empty SSID) and
     * ignore probe requests for broadcast SSID
     */
    int ignore_broadcast_ssid;

    /**
     * freq_list - Array of allowed frequencies or %NULL for all
     *
     * This is an optional zero-terminated array of frequencies in
     * megahertz (MHz) to allow for selecting the BSS. If set, scan results
     * that do not match any of the specified frequencies are not
     * considered when selecting a BSS.
     */
    int *freq_list;

    /**
     * p2p_client_list - List of P2P Clients in a persistent group (GO)
     *
     * This is a list of P2P Clients (P2P Device Address) that have joined
     * the persistent group. This is maintained on the GO for persistent
     * group entries (disabled == 2).
     */
    u8 *p2p_client_list;

    /**
     * num_p2p_clients - Number of entries in p2p_client_list
     */
    size_t num_p2p_clients;

#ifndef P2P_MAX_STORED_CLIENTS
#define P2P_MAX_STORED_CLIENTS 100
#endif /* P2P_MAX_STORED_CLIENTS */

    /**
     * psk_list - Per-client PSKs (struct psk_list_entry)
     */
    struct dl_list psk_list;

    /**
     * p2p_group - Network generated as a P2P group (used internally)
     */
    int p2p_group;

    /**
     * p2p_persistent_group - Whether this is a persistent group
     */
    int p2p_persistent_group;

    /**
     * temporary - Whether this network is temporary and not to be saved
     */
    int temporary;

    /**
     * export_keys - Whether keys may be exported
     *
     * This attribute will be set when keys are determined through
     * WPS or similar so that they may be exported.
     */
    int export_keys;

#ifdef ANDROID_P2P
    /**
     * assoc_retry - Number of times association should be retried.
     */
    int assoc_retry;
#endif

#ifdef CONFIG_HT_OVERRIDES
    /**
     * disable_ht - Disable HT (IEEE 802.11n) for this network
     *
     * By default, use it if it is available, but this can be configured
     * to 1 to have it disabled.
     */
    int disable_ht;

    /**
     * disable_ht40 - Disable HT40 for this network
     *
     * By default, use it if it is available, but this can be configured
     * to 1 to have it disabled.
     */
    int disable_ht40;

    /**
     * disable_sgi - Disable SGI (Short Guard Interval) for this network
     *
     * By default, use it if it is available, but this can be configured
     * to 1 to have it disabled.
     */
    int disable_sgi;

    /**
     * disable_max_amsdu - Disable MAX A-MSDU
     *
     * A-MDSU will be 3839 bytes when disabled, or 7935
     * when enabled (assuming it is otherwise supported)
     * -1 (default) means do not apply any settings to the kernel.
     */
    int disable_max_amsdu;

    /**
     * ampdu_factor - Maximum A-MPDU Length Exponent
     *
     * Value: 0-3, see 7.3.2.56.3 in IEEE Std 802.11n-2009.
     */
    int ampdu_factor;

    /**
     * ampdu_density - Minimum A-MPDU Start Spacing
     *
     * Value: 0-7, see 7.3.2.56.3 in IEEE Std 802.11n-2009.
     */
    int ampdu_density;

    /**
     * ht_mcs - Allowed HT-MCS rates, in ASCII hex: ffff0000...
     *
     * By default (empty string): Use whatever the OS has configured.
     */
    char *ht_mcs;
#endif /* CONFIG_HT_OVERRIDES */

#ifdef CONFIG_VHT_OVERRIDES
    /**
     * disable_vht - Disable VHT (IEEE 802.11ac) for this network
     *
     * By default, use it if it is available, but this can be configured
     * to 1 to have it disabled.
     */
    int disable_vht;

    /**
     * vht_capa - VHT capabilities to use
     */
    unsigned int vht_capa;

    /**
     * vht_capa_mask - mask for VHT capabilities
     */
    unsigned int vht_capa_mask;

    int vht_rx_mcs_nss_1, vht_rx_mcs_nss_2,
        vht_rx_mcs_nss_3, vht_rx_mcs_nss_4,
        vht_rx_mcs_nss_5, vht_rx_mcs_nss_6,
        vht_rx_mcs_nss_7, vht_rx_mcs_nss_8;
    int vht_tx_mcs_nss_1, vht_tx_mcs_nss_2,
        vht_tx_mcs_nss_3, vht_tx_mcs_nss_4,
        vht_tx_mcs_nss_5, vht_tx_mcs_nss_6,
        vht_tx_mcs_nss_7, vht_tx_mcs_nss_8;
#endif /* CONFIG_VHT_OVERRIDES */

    /**
     * ap_max_inactivity - Timeout in seconds to detect STA's inactivity
     *
     * This timeout value is used in AP mode to clean up inactive stations.
     * By default: 300 seconds.
     */
    int ap_max_inactivity;

    /**
     * dtim_period - DTIM period in Beacon intervals
     * By default: 2
     */
    int dtim_period;

    /**
     * beacon_int - Beacon interval (default: 100 TU)
     */
    int beacon_int;

    /**
     * auth_failures - Number of consecutive authentication failures
     */
    unsigned int auth_failures;

    /**
     * disabled_until - Network block disabled until this time if non-zero
     */
    struct os_time disabled_until;

    /**
     * parent_cred - Pointer to parent wpa_cred entry
     *
     * This pointer can be used to delete temporary networks when a wpa_cred
     * that was used to create them is removed. This pointer should not be
     * dereferences since it may not be updated in all cases.
     */
    void *parent_cred;
};