Squid zph-qos 選項

squid默認並不是以root用戶啓動的進程，而且即使設置爲以root用戶啓動也是無法生效的。

所以，如果想給socket打mark即調用setsockopt API函數的話需要權限來進行操作。

提權就很重要，libcap類庫就是來幹這個事情的。具體是在tools.cc文件中的函數實現restoreCapabilities 中CAP_NET_ADMIN就是提權的能力使能。

static void
restoreCapabilities(bool keep)
{
    /* NP: keep these two if-endif separate. Non-Linux work perfectly well without Linux syscap support. */
#if USE_LIBCAP
    cap_t caps;
    if (keep)
        caps = cap_get_proc();
    else
        caps = cap_init();
    if (!caps) {
        Ip::Interceptor.StopTransparency("Can't get current capabilities");
    } else {
        int ncaps = 0;
        int rc = 0;
        cap_value_t cap_list[10];
        cap_list[ncaps] = CAP_NET_BIND_SERVICE;
        ++ncaps;
        if (Ip::Interceptor.TransparentActive() ||
                Ip::Qos::TheConfig.isHitNfmarkActive() ||
                Ip::Qos::TheConfig.isAclNfmarkActive() ||
                Ip::Qos::TheConfig.isAclTosActive()) {
            cap_list[ncaps] = CAP_NET_ADMIN;
            ++ncaps;
        }

        cap_clear_flag(caps, CAP_EFFECTIVE);
        rc |= cap_set_flag(caps, CAP_EFFECTIVE, ncaps, cap_list, CAP_SET);
        rc |= cap_set_flag(caps, CAP_PERMITTED, ncaps, cap_list, CAP_SET);

        if (rc || cap_set_proc(caps) != 0) {
            Ip::Interceptor.StopTransparency("Error enabling needed capabilities.");
        }
        cap_free(caps);
    }
#elif _SQUID_LINUX_
    Ip::Interceptor.StopTransparency("Missing needed capability support.");
#endif /* HAVE_SYS_CAPABILITY_H */
}

zph 即Zero-Penalty Hit這個算法並不是真正意義上的Qos，而是基於命中的一種實現

Zero Penalty Hit created a patch to set QoS markers on outgoing traffic to clients.

Allows you to select a TOS/Diffserv value to mark local hits.
Allows you to select a TOS/Diffserv value to mark peer hits.
Allows you to selectively set only sibling or parent requests
Allows any HTTP response to clients will have the TOS value of the response coming from the remote server masked. For this to work correctly, you will need to patch your linux kernel with the TOS preserving ZPH patch. The kernel patch can be downloaded from http://zph.bratcheda.org
Allows you to mask certain bits in the TOS received from the remote server, before copying the value to the TOS send towards clients.

參考鏈接： http://wiki.squid-cache.org/Features/QualityOfService