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

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.