Question

根据来自：的代码 https://github.com/puzzlet/madwifi/blob/master/tools/wlanconfig.c#L565 struct iwreq曾经从80211驱动程序（例如站点列表）中获取信息，但是https://elixir.bootlin.com/linux/v4.0/source/include/uapi/linux/wireless.h#L685成员iwr.u.data.length (struct iw_point)表示__u16 length;有局限性>具有65535字节的最大值，代表数据的大小，指向void __user *pointer;。

我的下一个问题：如何通过iw_point正确传输数据，大于65535字节，（在Linux内核中是否有一些要求，例如IOCTL系统调用行为，或其他原因）标准化或基于驱动程序，我可以随意使用它，例如使用__u16 flags;？）。即如何标记void __user *pointer指向大小大于65535的内存？？

在struct iw_point的标题注释中显示注释，该数据可以大于65535字节，但是如何处理呢？

 /*
 *  For all data larger than 16 octets, we need to use a
 *  pointer to memory allocated in user space.
 */
struct  iw_point
{
  void __user   *pointer;   /* Pointer to the data  (in user space) */
  __u16     length;     /* number of fields or size in bytes */
  __u16     flags;      /* Optional params */
};

使用struct iwreq的函数示例（必须看到前20行）：

static void
list_stations(const char *ifname)
{
    uint8_t buf[24 * 1024];
    struct iwreq iwr;
    uint8_t *cp;
    int s, len;

    s = socket(AF_INET, SOCK_DGRAM, 0);
    if (s < 0)
        err(1, "socket(SOCK_DGRAM)");

    (void) memset(&iwr, 0, sizeof(iwr));
    (void) strncpy(iwr.ifr_name, ifname, sizeof(iwr.ifr_name));
    iwr.u.data.pointer = (void *)buf;
    iwr.u.data.length = sizeof(buf);
    if (ioctl(s, IEEE80211_IOCTL_STA_INFO, &iwr) < 0)
        errx(1, "unable to get station information");
    len = iwr.u.data.length;
    if (len < sizeof(struct ieee80211req_sta_info))
        return;
    close(s);

    printf("%-17.17s %4s %4s %4s %4s %4s %5s %6s %7s %6s %7s %4s %5s %3s %8s %8s\n",
        "ADDR",
        "AID",
        "CHAN",
        "RATE",
        "RSSI",
        "DBM",
        "IDLE",
        "TXSEQ",
        "TXFRAG",
        "RXSEQ",
        "RXFRAG",
        "CAPS",
        "ACAPS",
        "ERP",
        "STATE",
        "MODE");
    cp = buf;
    do {
        struct ieee80211req_sta_info *si;
        uint8_t *vp;

        si = (struct ieee80211req_sta_info *)cp;
        vp = (u_int8_t *)(si+1);
        printf("%s %4u %4d %3dM %4d %4d %5d %6d %7d %6d %7d %-4.4s %-5.5s %3x %8x %8s",
            ieee80211_ntoa(si->isi_macaddr),
            IEEE80211_AID(si->isi_associd),
            ieee80211_mhz2ieee(si->isi_freq),
            (si->isi_rates[si->isi_txrate] & IEEE80211_RATE_VAL) / 2,
            si->isi_rssi,
            rssi2dbm(si->isi_rssi),
            si->isi_inact,
            (si->isi_txseqs[0] & IEEE80211_SEQ_SEQ_MASK)
                >> IEEE80211_SEQ_SEQ_SHIFT,
            si->isi_txseqs[0] & IEEE80211_SEQ_FRAG_MASK,
            (si->isi_rxseqs[0] & IEEE80211_SEQ_SEQ_MASK)
                >> IEEE80211_SEQ_SEQ_SHIFT,
            si->isi_rxseqs[0] & IEEE80211_SEQ_FRAG_MASK,
                getcaps(si->isi_capinfo),
                getathcaps(si->isi_athflags),
            si->isi_erp,
            si->isi_state,
            getstamode(si->isi_opmode));
        printies(vp, si->isi_ie_len, 24);
        printf("\n");
        if (si->isi_uapsd) {
            printf("                   UAPSD QoSInfo: 0x%02x, ",
                si->isi_uapsd);
            printf("(VO,VI,BE,BK) = (%d,%d,%d,%d), MaxSpLimit = %s\n",
                   WME_UAPSD_AC_ENABLED(WME_AC_VO, si->isi_uapsd) ? 1 : 0,
                   WME_UAPSD_AC_ENABLED(WME_AC_VI, si->isi_uapsd) ? 1 : 0,
                   WME_UAPSD_AC_ENABLED(WME_AC_BE, si->isi_uapsd) ? 1 : 0,
                   WME_UAPSD_AC_ENABLED(WME_AC_BK, si->isi_uapsd) ? 1 : 0,
                   WME_UAPSD_MAXSP(si->isi_uapsd) == 1 ? "2" :
                   WME_UAPSD_MAXSP(si->isi_uapsd) == 2 ? "4" :
                   WME_UAPSD_MAXSP(si->isi_uapsd) == 3 ? "6" : "NoLimit");
        }
        cp += si->isi_len;
        len -= si->isi_len;
    } while (len >= sizeof(struct ieee80211req_sta_info));
}

如何通过大于65535字节的iw_point传递数据？

0 个答案: