通过研读Suricata入侵检测系统源代码学习SOCK_RAW原始套接字的使用方法

前言

Suricata是一套开源入侵检测系统, 其源代码可以通过github在线查看.

• https://github.com/OISF/suricata

关于AF_PACKET原始套接字的用法可以参考下列代码

• https://github.com/OISF/suricata/blob/master/src/source-af-packet.c#L2060-L2241

static int AFPCreateSocket(AFPThreadVars *ptv, char *devname, int verbose)
{
    int r;
    int ret = AFP_FATAL_ERROR;
    struct packet_mreq sock_params;
    struct sockaddr_ll bind_address;
    int if_idx;


    /* open socket */
    ptv->socket = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    if (ptv->socket == -1) {
        SCLogError(SC_ERR_AFP_CREATE, "Couldn't create a AF_PACKET socket, error %s", strerror(errno));
        goto error;
    }


    if_idx = AFPGetIfnumByDev(ptv->socket, devname, verbose);


    if (if_idx == -1) {
        goto socket_err;
    }


    /* bind socket */
    memset(&bind_address, 0, sizeof(bind_address));
    bind_address.sll_family = AF_PACKET;
    bind_address.sll_protocol = htons(ETH_P_ALL);
    bind_address.sll_ifindex = if_idx;
    if (bind_address.sll_ifindex == -1) {
        if (verbose)
            SCLogError(SC_ERR_AFP_CREATE, "Couldn't find iface %s", devname);
        ret = AFP_RECOVERABLE_ERROR;
        goto socket_err;
    }


    int if_flags = AFPGetDevFlags(ptv->socket, ptv->iface);
    if (if_flags == -1) {
        if (verbose) {
            SCLogError(SC_ERR_AFP_READ,
                    "Couldn't get flags for interface '%s'",
                    ptv->iface);
        }
        ret = AFP_RECOVERABLE_ERROR;
        goto socket_err;
    } else if ((if_flags & (IFF_UP | IFF_RUNNING)) == 0) {
        if (verbose) {
            SCLogError(SC_ERR_AFP_READ,
                    "Interface '%s' is down",
                    ptv->iface);
        }
        ret = AFP_RECOVERABLE_ERROR;
        goto socket_err;
    }


    if (ptv->promisc != 0) {
        /* Force promiscuous mode */
        memset(&sock_params, 0, sizeof(sock_params));
        sock_params.mr_type = PACKET_MR_PROMISC;
        sock_params.mr_ifindex = bind_address.sll_ifindex;
        r = setsockopt(ptv->socket, SOL_PACKET, PACKET_ADD_MEMBERSHIP,(void *)&sock_params, sizeof(sock_params));
        if (r < 0) {
            SCLogError(SC_ERR_AFP_CREATE,
                    "Couldn't switch iface %s to promiscuous, error %s",
                    devname, strerror(errno));
            goto socket_err;
        }
    }


    if (ptv->checksum_mode == CHECKSUM_VALIDATION_KERNEL) {
        int val = 1;
        if (setsockopt(ptv->socket, SOL_PACKET, PACKET_AUXDATA, &val,
                    sizeof(val)) == -1 && errno != ENOPROTOOPT) {
            SCLogWarning(SC_ERR_NO_AF_PACKET,
                         "'kernel' checksum mode not supported, falling back to full mode.");
            ptv->checksum_mode = CHECKSUM_VALIDATION_ENABLE;
        }
    }


    /* set socket recv buffer size */
    if (ptv->buffer_size != 0) {
        /*
         * Set the socket buffer size to the specified value.
         */
        SCLogPerf("Setting AF_PACKET socket buffer to %d", ptv->buffer_size);
        if (setsockopt(ptv->socket, SOL_SOCKET, SO_RCVBUF,
                       &ptv->buffer_size,
                       sizeof(ptv->buffer_size)) == -1) {
            SCLogError(SC_ERR_AFP_CREATE,
                    "Couldn't set buffer size to %d on iface %s, error %s",
                    ptv->buffer_size, devname, strerror(errno));
            goto socket_err;
        }
    }


    r = bind(ptv->socket, (struct sockaddr *)&bind_address, sizeof(bind_address));
    if (r < 0) {
        if (verbose) {
            if (errno == ENETDOWN) {
                SCLogError(SC_ERR_AFP_CREATE,
                        "Couldn't bind AF_PACKET socket, iface %s is down",
                        devname);
            } else {
                SCLogError(SC_ERR_AFP_CREATE,
                        "Couldn't bind AF_PACKET socket to iface %s, error %s",
                        devname, strerror(errno));
            }
        }
        ret = AFP_RECOVERABLE_ERROR;
        goto socket_err;
    }




#ifdef HAVE_PACKET_FANOUT
    /* add binded socket to fanout group */
    if (ptv->threads > 1) {
        uint16_t mode = ptv->cluster_type;
        uint16_t id = ptv->cluster_id;
        uint32_t option = (mode << 16) | (id & 0xffff);
        r = setsockopt(ptv->socket, SOL_PACKET, PACKET_FANOUT,(void *)&option, sizeof(option));
        if (r < 0) {
            SCLogError(SC_ERR_AFP_CREATE,
                       "Couldn't set fanout mode, error %s",
                       strerror(errno));
            goto socket_err;
        }
    }
#endif


#ifdef HAVE_PACKET_EBPF
    if (ptv->cluster_type == PACKET_FANOUT_EBPF) {
        r = SockFanoutSeteBPF(ptv);
        if (r < 0) {
            SCLogError(SC_ERR_AFP_CREATE,
                       "Coudn't set EBPF, error %s",
                       strerror(errno));
            goto socket_err;
        }
    }
#endif


    if (ptv->flags & AFP_RING_MODE) {
        ret = AFPSetupRing(ptv, devname);
        if (ret != 0)
            goto socket_err;
    }


    SCLogDebug("Using interface '%s' via socket %d", (char *)devname, ptv->socket);


    ptv->datalink = AFPGetDevLinktype(ptv->socket, ptv->iface);
    switch (ptv->datalink) {
        case ARPHRD_PPP:
        case ARPHRD_ATM:
            ptv->cooked = 1;
            break;
    }


    TmEcode rc = AFPSetBPFFilter(ptv);
    if (rc == TM_ECODE_FAILED) {
        ret = AFP_FATAL_ERROR;
        goto socket_err;
    }


    /* Init is ok */
    AFPSwitchState(ptv, AFP_STATE_UP);
    return 0;


socket_err:
    close(ptv->socket);
    ptv->socket = -1;
    if (ptv->flags & AFP_TPACKET_V3) {
        if (ptv->ring.v3) {
            SCFree(ptv->ring.v3);
            ptv->ring.v3 = NULL;
        }
    } else {
        if (ptv->ring.v2) {
            SCFree(ptv->ring.v2);
            ptv->ring.v2 = NULL;
        }
    }


error:
    return -ret;
}

• 官方网站https://suricata-ids.org/download/