Android Wi-Fi源码分析之wpa_supplicant初始化(三):wpa_supplicant_add_iface函数分析

路径为: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;    }    /* 通过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;    }    /*通过dbus通知外界有新的无线网络加入*/    for (ssid = wpa_s->conf->ssid; ssid; ssid = ssid->next)        wpas_notify_network_added(wpa_s, ssid);    /* wpa_global的ifaces变量指向一个wpa_supplicant对象,     * 而wpa_supplicant又通过next变量将自己链接到一个单项链表中*/    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函数的内容非常丰富, 包括两个重要数据结构(wpa_supplicant和wpa_ssid)以及一个关键函数wpa_supplicant_init_iface.这些数据背景较多, 先来看看他们.

wpa_ssid结构体

wpa_ssid结构体用于存储某个无线网络的配置信息(如所支持的安全类型, 优先级等). (external\wpa_supplicant_8\wpa_supplicant\wpa_supplicant.conf)文件中的每一个network项都对应一个wpa_ssid对象.
路径为: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对象都保存在一个链表当中, 头指针保存于另外一个结构体wpa_config的ssid变量中*/    /**     * 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还可以按priority保存在另一个链表中, 头指针为wpa_config的ssid变量*/    /**     * 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;/*每个无线网络都有一个唯一的编号*/    /**     * 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;/*该无线网络对应的priority值, 默认为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;/*无线网络的名字*/    /**     * ssid_len - Length of the SSID     */    size_t ssid_len;/*ssid变量长度*/    /**     * 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];/*用于保存bssid[ETH_ALEN]*/    /**     * bssid_set - Whether BSSID is configured for this network     */    int bssid_set;/*该无线网络是否设置了bssid变量*/    /**     * psk - WPA pre-shared key (256 bits)     */    u8 psk[32];/*数组长度为32, 用于保存WPA中的Pre-Shared Key (256位)*/    /**     * psk_set - Whether PSK field is configured     */    int psk_set;/*是否设置了上面的psk参数*/    /**     * 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;/*为WPA设置ASCII字符密码*/    /**     * 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;/*用于单播数据加密的密钥类型*/    /**     * group_cipher - Bitfield of allowed group ciphers, WPA_CIPHER_*     */    int group_cipher;/*用于数组数据加密的密钥类型*/    /**     * key_mgmt - Bitfield of allowed key management protocols     *     * WPA_KEY_MGMT_*     */    int key_mgmt;/*密钥管理类型*/    /**     * 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;/*该无线网络支持的安全保护类型*/    /**     * auth_alg -  Bitfield of allowed authentication algorithms     *     * WPA_AUTH_ALG_*     */    int auth_alg;/*该无线网络支持的身份验证类型*/    /**     * 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帧扫描此ssid对应的无线网络*/#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选项*/    /**     * eap - EAP peer configuration for this network     */    struct eap_peer_config eap;/*eap peer端设置信息*/#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;};