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Re: [libvirt] [PATCH v5] network: bridge: Don't start network if it collides with host routing



On 05/27/2010 05:09 PM, Jim Meyering wrote:
> Cole Robinson wrote:
>> Fedora bug https://bugzilla.redhat.com/show_bug.cgi?id=235961
>>
>> If using the default virtual network, an easy way to lose guest network
>> connectivity is to install libvirt inside the VM. The autostarted
>> default network inside the guest collides with host virtual network
>> routing. This is a long standing issue that has caused users quite a
>> bit of pain and confusion.
>>
>> On network startup, parse /proc/net/route and compare the requested
>> IP+netmask against host routing destinations: if any matches are found,
>> refuse to start the network.
>>
>> v2: Drop sscanf, fix a comment typo, comment that function could use
>>     libnl instead of /proc
>>
>> v3: Consider route netmask. Compare binary data rather than convert to
>>     string.
>>
>> v4: Return to using sscanf, drop inet functions in favor of virSocket,
>>     parsing safety checks. Don't make parse failures fatal, in case
>>     expected format changes.
>>
>> v5: Try and continue if we receive unexpected. Delimit parsed lines to
>>     prevent scanning past newline
> ...
>> +    while (cur) {
>> +        char iface[17], dest[128], mask[128];
>> +        unsigned int addr_val, mask_val;
>> +        int num;
>> +
>> +        /* NUL-terminate the line, so sscanf doesn't go beyond a newline.  */
>> +        char *nl = strchr(cur, '\n');
>> +        if (nl) {
>> +            *nl++ = '\0';
>> +        }
>> +
>> +        num = sscanf(cur, "%16s %127s %*s %*s %*s %*s %*s %127s",
>> +                     iface, dest, mask);
>> +        cur = nl;
> 
> Glad you incremented nl above and hoisted the "cur" update to here.
> 
> ACK.

Thanks, I've pushed this now.

- Cole


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