Add a "fork" of musl as //fusl.

fusl/src/network/getservbyport_r.c

+#define _GNU_SOURCE
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <string.h>
+
+int getservbyport_r(int port, const char *prots,
+        struct servent *se, char *buf, size_t buflen, struct servent **res)
+{
+        int i;
+        struct sockaddr_in sin = {
+                .sin_family = AF_INET,
+                .sin_port = port,
+        };
+
+        if (!prots) {
+                int r = getservbyport_r(port, "tcp", se, buf, buflen, res);
+                if (r) r = getservbyport_r(port, "udp", se, buf, buflen, res);
+                return r;
+        }
+
+        /* Align buffer */
+        i = (uintptr_t)buf & sizeof(char *)-1;
+        if (!i) i = sizeof(char *);
+        if (buflen < 3*sizeof(char *)-i)
+                return ERANGE;
+        buf += sizeof(char *)-i;
+        buflen -= sizeof(char *)-i;
+
+        if (strcmp(prots, "tcp") && strcmp(prots, "udp")) return EINVAL;
+
+        se->s_port = port;
+        se->s_proto = (char *)prots;
+        se->s_aliases = (void *)buf;
+        buf += 2*sizeof(char *);
+        buflen -= 2*sizeof(char *);
+        se->s_aliases[1] = 0;
+        se->s_aliases[0] = se->s_name = buf;
+
+        switch (getnameinfo((void *)&sin, sizeof sin, 0, 0, buf, buflen,
+                strcmp(prots, "udp") ? 0 : NI_DGRAM)) {
+        case EAI_MEMORY:
+        case EAI_SYSTEM:
+                return ENOMEM;
+        default:
+                return ENOENT;
+        case 0:
+                break;
+        }
+
+        *res = se;
+        return 0;
+}