v4.19.13 snapshot.
diff --git a/net/ipv4/metrics.c b/net/ipv4/metrics.c
new file mode 100644
index 0000000..04311f7
--- /dev/null
+++ b/net/ipv4/metrics.c
@@ -0,0 +1,55 @@
+#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>
+
+int ip_metrics_convert(struct net *net, struct nlattr *fc_mx, int fc_mx_len,
+ u32 *metrics)
+{
+ 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)
+ 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)
+ return -EINVAL;
+ } else {
+ if (nla_len(nla) != sizeof(u32))
+ 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))
+ return -EINVAL;
+ metrics[type - 1] = val;
+ }
+
+ if (ecn_ca)
+ metrics[RTAX_FEATURES - 1] |= DST_FEATURE_ECN_CA;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(ip_metrics_convert);