Teach nut-scanner -m auto*/ADDRLEN modes

[jimklimov]

Follow-up for PRs #2509 and #2513, of issue #2244.

This PR adds a way to constrain the scan amounts in discovered subnets by specifying the bit-width of the host address part (e.g. in a typical IPv4 /24 subnet, that part of the option value would be 32-24 = 8 => -m auto4/8).

Also it now reports detailed reasons why this or that discovered subnet was ignored (too large, loopback, not up and running...)

Detailed "screenshot" from a test run:

:; make -ks -j && LD_LIBRARY_PATH=`pwd`/clients/.libs ./tools/nut-scanner/nut-scanner -DDDDDD -O -m auto4/4
...
   0.080064     [D5] Discovering getifaddrs(): Interface: lo    Address: 127.0.0.1      Mask: 255.0.0.0 (subnet: 8, hosts: 24)  Flags: 00010049 IFF_LOOPBACK IFF_UP IFF_RUNNING
   0.080106     [D6] Subnet ignored: address range too large: 4 bits allowed vs. 24 bits per netmask
   0.080138     [D5] Discovering getifaddrs(): Interface: eth0  Address: 172.28.79.185  Mask: 255.255.240.0 (subnet: 20, hosts: 12)     Flags: 00011043 IFF_UP IFF_RUNNING IFF_BROADCAST(is assigned)
   0.080145     [D6] Subnet ignored: address range too large: 4 bits allowed vs. 12 bits per netmask
   0.080148     [D5] Discovering getifaddrs(): Interface: eth0  Address: 172.22.48.99   Mask: 255.255.240.0 (subnet: 20, hosts: 12)     Flags: 00011043 IFF_UP IFF_RUNNING IFF_BROADCAST(is assigned)
   0.080156     [D6] Subnet ignored: address range too large: 4 bits allowed vs. 12 bits per netmask
   0.080163     [D5] Discovering getifaddrs(): Interface: lo    Address: ::1    Mask: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff (subnet: 128, hosts: 0)   Flags: 00010049 IFF_LOOPBACK IFF_UP IFF_RUNNING
   0.080188     [D6] Subnet ignored: loopback
   0.080218     [D5] Discovering getifaddrs(): Interface: eth0  Address: fe80::215:5dff:fe8b:d950%eth0  Mask: ffff:ffff:ffff:ffff:: (subnet: 64, hosts: 64)     Flags: 00011043 IFF_UP IFF_RUNNING IFF_BROADCAST(is assigned)
   0.080250     [D6] Subnet ignored: address range too large: 4 bits allowed vs. 64 bits per netmask
...

And with -m auto4/16 it did accept some of the address ranges:

   0.065008     [D5] Discovering getifaddrs(): Interface: lo    Address: 127.0.0.1      Mask: 255.0.0.0 (subnet: 8, hosts: 24)  Flags: 00010049 IFF_LOOPBACK IFF_UP IFF_RUNNING
   0.065029     [D6] Subnet ignored: address range too large: 16 bits allowed vs. 24 bits per netmask
   0.065067     [D5] Discovering getifaddrs(): Interface: eth0  Address: 172.28.79.185  Mask: 255.255.240.0 (subnet: 20, hosts: 12)     Flags: 00011043 IFF_UP IFF_RUNNING IFF_BROADCAST(is assigned)
   0.065088     [D5] Processing CIDR net/mask: 172.28.79.185/20
   0.065092     [D5] nutscan_cidr_to_ip: parsed cidr=172.28.79.185/20 into first_ip=172.28.79.185 and mask=20
   0.065094     [D5] nutscan_cidr_to_ip: parsed mask into numeric value 20
   0.065097     [D5] Extracted IP address range from CIDR net/mask: 172.28.64.0 => 172.28.79.255
   0.065099     [D1] Recorded IP address range #1: [172.28.64.0 .. 172.28.79.255]
   0.065122     [D5] Discovering getifaddrs(): Interface: eth0  Address: 172.22.48.99   Mask: 255.255.240.0 (subnet: 20, hosts: 12)     Flags: 00011043 IFF_UP IFF_RUNNING IFF_BROADCAST(is assigned)
   0.065143     [D5] Processing CIDR net/mask: 172.22.48.99/20
   0.065147     [D5] nutscan_cidr_to_ip: parsed cidr=172.22.48.99/20 into first_ip=172.22.48.99 and mask=20
   0.065165     [D5] nutscan_cidr_to_ip: parsed mask into numeric value 20
   0.065170     [D5] Extracted IP address range from CIDR net/mask: 172.22.48.0 => 172.22.63.255
   0.065191     [D1] Recorded IP address range #2: [172.22.48.0 .. 172.22.63.255]
   0.065199     [D5] Discovering getifaddrs(): Interface: lo    Address: ::1    Mask: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff (subnet: 128, hosts: 0)   Flags: 00010049 IFF_LOOPBACK IFF_UP IFF_RUNNING
   0.065217     [D6] Subnet ignored: loopback
   0.066865     [D5] Discovering getifaddrs(): Interface: eth0  Address: fe80::215:5dff:fe8b:d950%eth0  Mask: ffff:ffff:ffff:ffff:: (subnet: 64, hosts: 64)     Flags: 00011043 IFF_UP IFF_RUNNING IFF_BROADCAST(is assigned)
   0.066893     [D6] Subnet ignored: address range too large: 16 bits allowed vs. 64 bits per netmask

I've initially considered adding (also?) a mode for layman users to request the amount of scans they would tolerate, e.g. -m auto4#200 that would translate into "200 < 256 => bit length 8 or less is okay for host address part", but per https://stackoverflow.com/questions/466204/rounding-up-to-next-power-of-2 it is not too trivial - and for IPv6 support to be on par across the board, some fiddling with uint128_t (not ubiquitous) would be needed.

[jimklimov]

Testing erroneous-input checking:

• -m autox is let slide:

   0.065437     Got a '-m auto*' CLI option with unsupported keyword pattern; assuming a CIDR, likely to fail: autox
   0.065468     [D5] Processing CIDR net/mask: autox
   0.065472     WARNING: nutscan_cidr_to_ip failed to parse mask from cidr=autox (first_ip=autox)
   0.065474     [D5] Extracted IP address range from CIDR net/mask: (null) => (null)
   0.065476     [D5] add_ip_range: skip, no addresses were provided

• -m auto/x is fatal:

...
   0.077328     Invalid auto-net limit value, should be an integer [0..128]: auto/x

$ echo $?
1

• -m auto/146 (bit length too long) also:

   0.064268     Invalid auto-net limit value, should be an integer [0..128]: auto/146

UPDATE: Using strtol() allows for finer-grained checks of invalid input instead of atol() just returning 0, e.g.

   0.072813     [D6] errno=0 s=''(0x7ffc11358000) input='129'(0x7ffc11357ffd) output=129
   0.072835     Invalid auto-net limit value, should be an integer [0..128]: auto/129

   0.087820     [D6] errno=0 s='x'(0x7ffe7d038fff) input='4x'(0x7ffe7d038ffe) output=4
   0.087845     Invalid auto-net limit value, should be an integer [0..128]: auto/4x

   0.079053     [D6] errno=0 s=''(0x7ffee9e67000) input='4'(0x7ffee9e66fff) output=4
   0.079151     [D5] Discovering getifaddrs(): Interface: lo    Address: 127.0.0.1      Mask: 255.0.0.0 (subnet: 8, hosts: 24)  Flags: 00010049 IFF_LOOPBACK IFF_UP IFF_RUNNING
   0.079173     [D6] Subnet ignored: address range too large: 4 bits allowed vs. 24 bits per netmask
...

[AppVeyorBot]

✅ Build nut 2.8.2.1889-master completed (commit fc5e3466ed by @jimklimov)

[jimklimov]

Exposed the code for IP range lists tracking as part of libnutscan so it can be used elsewhere (preparing for #2511 in particular).

[AppVeyorBot]

❌ Build nut 2.8.2.1895-master failed (commit 0488fac52f by @jimklimov)