Replace my C code with tianons Go code

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

pkg/netlink/netlink_linux.go

@@ -2,60 +2,6 @@
 
 package netlink
 
-/*
-#include <string.h>
-#include <errno.h>
-#include <sys/ioctl.h>
-#include <net/if.h>
-
-static int get_socket(void) {
-	int s_errno;
-	int fd;
-
-	fd = socket(PF_INET, SOCK_DGRAM, 0);
-	if (fd >= 0) {
-		return fd;
-    }
-	s_errno = errno;
-
-	fd = socket(PF_PACKET, SOCK_DGRAM, 0);
-	if (fd >= 0) {
-		return fd;
-    }
-
-	fd = socket(PF_INET6, SOCK_DGRAM, 0);
-	if (fd >= 0) {
-		return fd;
-    }
-	errno = s_errno;
-	return -1;
-}
-
-
-static int change_name(const char *old_name, const char *new_name) {
-    struct ifreq ifr;
-	int err;
-	int fd;
-
-	fd = get_socket();
-	if (fd < 0) {
-		return -1;
-    }
-
-	strncpy(ifr.ifr_name, old_name, IFNAMSIZ);
-	strncpy(ifr.ifr_newname, new_name, IFNAMSIZ);
-
-    err = ioctl(fd, SIOCSIFNAME, &ifr);
-	if (err) {
-        close(fd);
-		return -1;
-	}
-    close(fd);
-	return err;
-}
-*/
-import "C"
-
 import (
 	"encoding/binary"
 	"fmt"
@@ -696,14 +642,41 @@ done:
 	return res, nil
 }
 
+func getIfSocket() (int, error) {
+	fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_DGRAM, 0)
+	if err == nil {
+		return fd, err
+	}
+	sErr := err
+
+	fd, err = syscall.Socket(syscall.AF_PACKET, syscall.SOCK_DGRAM, 0)
+	if err == nil {
+		return fd, err
+	}
+
+	fd, err = syscall.Socket(syscall.AF_INET6, syscall.SOCK_DGRAM, 0)
+	if err == nil {
+		return fd, err
+	}
+
+	return -1, sErr
+}
+
 func NetworkChangeName(oldName, newName string) error {
-	var (
-		cold = C.CString(oldName)
-		cnew = C.CString(newName)
-	)
+	fd, err := getIfSocket()
+	if err != nil {
+		return err
+	}
+	defer syscall.Close(fd)
+	IFNAMSIZ := 16
+
+	data := [32]byte{}
+	copy(data[:IFNAMSIZ-1], oldName)
+	copy(data[IFNAMSIZ:IFNAMSIZ*2-1], newName)
 
-	if errno := int(C.change_name(cold, cnew)); errno != 0 {
-		return fmt.Errorf("unable to change name %d", errno)
+	if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), syscall.SIOCSIFNAME, uintptr(unsafe.Pointer(&data[0]))); errno != 0 {
+		return errno
 	}
+
 	return nil
 }