1 /*
2  * Copyright 2021 Google LLC
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #include <inttypes.h>
18 #include <linux/if_ether.h>
19 #include <net/ethernet.h>
20 #include <stdio.h>
21 
22 #define ETH_STRLEN (ETH_ALEN * 3)
23 #define HEX_OUT "%02" PRIx8
24 #define ETH_OUT                                                                \
25     HEX_OUT ":" HEX_OUT ":" HEX_OUT ":" HEX_OUT ":" HEX_OUT ":" HEX_OUT
26 #define HEX_IN "%2" SCNx8
27 #define ETH_IN HEX_IN ":" HEX_IN ":" HEX_IN ":" HEX_IN ":" HEX_IN ":" HEX_IN
28 
29 int to_ether_addr(const char* str, struct ether_addr* ret)
30 {
31     char sentinel;
32     return sscanf(str, ETH_IN "%c", &ret->ether_addr_octet[0],
33                   &ret->ether_addr_octet[1], &ret->ether_addr_octet[2],
34                   &ret->ether_addr_octet[3], &ret->ether_addr_octet[4],
35                   &ret->ether_addr_octet[5], &sentinel) != ETH_ALEN;
36 }
37 
38 void from_ether_addr(const struct ether_addr* addr, char* ret)
39 {
40     sprintf(ret, ETH_OUT, addr->ether_addr_octet[0], addr->ether_addr_octet[1],
41             addr->ether_addr_octet[2], addr->ether_addr_octet[3],
42             addr->ether_addr_octet[4], addr->ether_addr_octet[5]);
43 }
44 
45 int main(int argc, char* argv[])
46 {
47     if (argc < 1)
48     {
49         return 1;
50     }
51     if (argc != 2)
52     {
53         fprintf(stderr, "Usage: %s <mac address>\n", argv[0]);
54         return 1;
55     }
56 
57     struct ether_addr addr;
58     if (to_ether_addr(argv[1], &addr) != 0)
59     {
60         fprintf(stderr, "Invalid MAC Address: %s\n", argv[1]);
61         return 2;
62     }
63 
64     char str[ETH_STRLEN];
65     from_ether_addr(&addr, str);
66     printf("%s\n", str);
67     return 0;
68 }
69