[libvirt] [PATCH 1/2] util: Functions to update host network device's multicast filter

[Eric Blake]

On 10/08/2014 09:36 AM, Laine Stump wrote:
> On 10/06/2014 05:37 PM, akrowiak at linux.vnet.ibm.com wrote:
>> From: Tony Krowiak <akrowiak at linux.vnet.ibm.com>
>>
>> This patch provides the utility functions to needed to synchronize the
>> changes made to a guest domain network device's multicast filter
>> with the corresponding macvtap device's filter on the host:
>>
>> * Get/add/remove multicast MAC addresses
>> * Get the macvtap device's RX filter list
>>
>> Signed-off-by: Tony Krowiak <akrowiak at linux.vnet.ibm.com>
>> ---

>> +/**
>> + * virMacAddrParseHex:
>> + * @str: string hexadecimal representation of MAC address, e.g., "F801EFCE3aCB"
>> + * @addr: 6-byte MAC address
>> + *
>> + * Parse the hexadecimal representation of a MAC address
>> + *
>> + * Return 0 upon success, or -1 in case of error.
>> + */
>> +int
>> +virMacAddrParseHex(const char* str, virMacAddrPtr addr)

Wrong spacing around '*'.

>> +{
>> +    if (strlen(str) != VIR_MAC_HEXLEN)
>> +        return -1;
>> +
>> +    size_t iaddr;
>> +    size_t istr;
>> +
>> +
>> +    for (istr = 0, iaddr = 0; iaddr < VIR_MAC_BUFLEN; istr += 2, iaddr++) {
>> +        unsigned int hex;
>> +
>> +        if (sscanf(&str[istr], "%02x", &hex) != 1)
>> +            break;
> 
> I'm not keen on sscanf(), but since we're already using it elsewhere,
> and the existing virMacAddrParse uses the normally-blacklisted strtoul()
> (and using virStrToLong_ui() on pieces of the string would require a
> terminating character after each piece), I don't have a ready answer for
> an alternative.

Why not just open-code it?  It's just two input bytes per iteration, and
we already have a helper function that makes it a very short function.
And strspn makes it easy to do input validation before starting the loop:

int
virMacAddrParseHex(const char *str, virMacAddrPtr addr)
{
    size_t i;

    if (strspn(str, "0123456789abcdefABCDEF") != VIR_MAC_HEXLEN ||
        str[VIR_MAC_HEXLEN])
        return -1;

    for (i = 0; i < VIR_MAC_BUFLEN; i++)
        addr->addr[i] = (virHexToBin(str[2 * i]) << 4 |
                         virHexToBin(str[2 * i + 1]));
    return 0;
}

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 539 bytes
Desc: OpenPGP digital signature
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20141008/335087c8/attachment-0001.sig>