对于这个消息的具体处理：

static enum ofperr
handle_set_config(struct ofconn *ofconn, const struct ofp_header *oh)
{
    const struct ofp_switch_config *osc = ofpmsg_body(oh);
     /* ignore the ofp_header to get the config struct */
    struct ofproto *ofproto = ofconn_get_ofproto(ofconn);
     /*get the OF SW abstraction, later will config it */
    uint16_t flags = ntohs(osc->flags);
     /*openflow use bigendian mode*/

    if (ofconn_get_type(ofconn) != OFCONN_PRIMARY
        || ofconn_get_role(ofconn) != NX_ROLE_SLAVE) {
        enum ofp_config_flags cur = ofproto->frag_handling;
        enum ofp_config_flags next = flags & OFPC_FRAG_MASK;

        assert((cur & OFPC_FRAG_MASK) == cur);
        if (cur != next) {
            if (ofproto->ofproto_class->set_frag_handling(ofproto, next)) {
                ofproto->frag_handling = next;
            } else {
                VLOG_WARN_RL(&rl, "%s: unsupported fragment handling mode %s",
                             ofproto->name,
                             ofputil_frag_handling_to_string(next));
            }
        }
    }
    ofconn_set_invalid_ttl_to_controller(ofconn,
             (flags & OFPC_INVALID_TTL_TO_CONTROLLER));
     /* set the max miss length of the SW XXX*/
    ofconn_set_miss_send_len(ofconn, ntohs(osc->miss_send_len));

    return 0;
}

下面的这个结构体代表的是 OFPT_SET_CONFIG 消息的消息体。

/* Switch configuration. */
struct ofp_switch_config {
    ovs_be16 flags;             /* OFPC_* flags. */
    ovs_be16 miss_send_len;     /* Max bytes of new flow that datapath should
                                   send to the controller. */
};
OFP_ASSERT(sizeof(struct ofp_switch_config) == 4);

Floodlight 是如何发送这个消息的呢？ 比如 设置在出现packetin时候把全部的包发送到 Controller。

OFSetConfig config = (OFSetConfig) factory
                    .getMessage(OFType.SET_CONFIG);
            config.setMissSendLength((short) 0xffff)
            .setLengthU(OFSwitchConfig.MINIMUM_LENGTH);
            sw.write(config, null);