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gen_ethaddr_crc.c 1.65 KiB
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  • /*
     * (C) Copyright 2016
     * Olliver Schinagl <oliver@schinagl.nl>
     *
     * SPDX-License-Identifier:	GPL-2.0+
     */
    
    #include <ctype.h>
    #include <stdint.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <u-boot/crc.h>
    
    #define ARP_HLEN 6 /* Length of hardware address */
    #define ARP_HLEN_ASCII (ARP_HLEN * 2) + (ARP_HLEN - 1) /* with separators */
    #define ARP_HLEN_LAZY (ARP_HLEN * 2) /* separatorless hardware address length */
    
    uint8_t nibble_to_hex(const char *nibble, bool lo)
    {
    	return (strtol(nibble, NULL, 16) << (lo ? 0 : 4)) & (lo ? 0x0f : 0xf0);
    }
    
    int process_mac(const char *mac_address)
    {
    	uint8_t ethaddr[ARP_HLEN + 1] = { 0x00 };
    	uint_fast8_t i = 0;
    
    	while (*mac_address != '\0') {
    		char nibble[2] = { 0x00, '\n' }; /* for strtol */
    
    		nibble[0] = *mac_address++;
    		if (isxdigit(nibble[0])) {
    			if (isupper(nibble[0]))
    				nibble[0] = tolower(nibble[0]);
    			ethaddr[i >> 1] |= nibble_to_hex(nibble, (i % 2) != 0);
    			i++;
    		}
    	}
    
    	for (i = 0; i < ARP_HLEN; i++)
    		printf("%.2x", ethaddr[i]);
    	printf("%.2x\n", crc8(0, ethaddr, ARP_HLEN));
    
    	return 0;
    }
    
    void print_usage(char *cmdname)
    {
    	printf("Usage: %s <mac_address>\n", cmdname);
    	puts("<mac_address> may be with or without separators.");
    	puts("Valid seperators are ':' and '-'.");
    	puts("<mac_address> digits are in base 16.\n");
    }
    
    int main(int argc, char *argv[])
    {
    	if (argc < 2) {
    		print_usage(argv[0]);
    		return 1;
    	}
    
    	if (!((strlen(argv[1]) == ARP_HLEN_ASCII) || (strlen(argv[1]) == ARP_HLEN_LAZY))) {
    		puts("The MAC address is not valid.\n");
    		print_usage(argv[0]);
    		return 1;
    	}
    
    	if (process_mac(argv[1])) {
    		puts("Failed to calculate the MAC's checksum.");
    		return 1;
    	}
    
    	return 0;
    }