// SPDX-License-Identifier: GPL-2.0-only

  #include <linux/netlink.h>
  #include <linux/rtnetlink.h>
  #include <linux/types.h>
  #include <net/ip.h>
  #include <net/net_namespace.h>
  #include <net/tcp.h>

  static int ip_metrics_convert(struct net *net, struct nlattr *fc_mx,

  			      int fc_mx_len, u32 *metrics,
  			      struct netlink_ext_ack *extack)

  {
  	bool ecn_ca = false;
  	struct nlattr *nla;
  	int remaining;
  
  	if (!fc_mx)
  		return 0;
  
  	nla_for_each_attr(nla, fc_mx, fc_mx_len, remaining) {
  		int type = nla_type(nla);
  		u32 val;
  
  		if (!type)
  			continue;

  		if (type > RTAX_MAX) {
  			NL_SET_ERR_MSG(extack, "Invalid metric type");

  			return -EINVAL;

  		}

  
  		if (type == RTAX_CC_ALGO) {
  			char tmp[TCP_CA_NAME_MAX];
  
  			nla_strlcpy(tmp, nla, sizeof(tmp));
  			val = tcp_ca_get_key_by_name(net, tmp, &ecn_ca);

  			if (val == TCP_CA_UNSPEC) {
  				NL_SET_ERR_MSG(extack, "Unknown tcp congestion algorithm");

  				return -EINVAL;

  			}

  		} else {

  			if (nla_len(nla) != sizeof(u32)) {
  				NL_SET_ERR_MSG_ATTR(extack, nla,
  						    "Invalid attribute in metrics");

  				return -EINVAL;

  			}

  			val = nla_get_u32(nla);
  		}
  		if (type == RTAX_ADVMSS && val > 65535 - 40)
  			val = 65535 - 40;
  		if (type == RTAX_MTU && val > 65535 - 15)
  			val = 65535 - 15;
  		if (type == RTAX_HOPLIMIT && val > 255)
  			val = 255;

  		if (type == RTAX_FEATURES && (val & ~RTAX_FEATURE_MASK)) {
  			NL_SET_ERR_MSG(extack, "Unknown flag set in feature mask in metrics attribute");

  			return -EINVAL;

  		}

  		metrics[type - 1] = val;
  	}
  
  	if (ecn_ca)
  		metrics[RTAX_FEATURES - 1] |= DST_FEATURE_ECN_CA;
  
  	return 0;
  }

  
  struct dst_metrics *ip_fib_metrics_init(struct net *net, struct nlattr *fc_mx,

  					int fc_mx_len,
  					struct netlink_ext_ack *extack)

  {
  	struct dst_metrics *fib_metrics;
  	int err;
  
  	if (!fc_mx)
  		return (struct dst_metrics *)&dst_default_metrics;
  
  	fib_metrics = kzalloc(sizeof(*fib_metrics), GFP_KERNEL);
  	if (unlikely(!fib_metrics))
  		return ERR_PTR(-ENOMEM);

  	err = ip_metrics_convert(net, fc_mx, fc_mx_len, fib_metrics->metrics,
  				 extack);

  	if (!err) {
  		refcount_set(&fib_metrics->refcnt, 1);
  	} else {
  		kfree(fib_metrics);
  		fib_metrics = ERR_PTR(err);
  	}
  
  	return fib_metrics;
  }
  EXPORT_SYMBOL_GPL(ip_fib_metrics_init);