Date: Fri, 12 Feb 2016 08:53:09 +0800 From: Julian Elischer <julian@freebsd.org> To: Jeremy Boy <jb@jboy.eu>, freebsd-net@freebsd.org Subject: Re: ifconfig with quoted arguments Message-ID: <56BD2CF5.7020200@freebsd.org> In-Reply-To: <76A08658-ACD2-426B-865A-45A6A79BBFB4@jboy.eu> References: <76A08658-ACD2-426B-865A-45A6A79BBFB4@jboy.eu>
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On 10/02/2016 5:51 AM, Jeremy Boy wrote: > Hello list, > > please CC me in replies to this mail, since I am no subscriber to this list. > > For safety reasons, we enclose user input to shell commands in quotes. Until today, the resulting command for ifconfig(8) looked like this: > >> ifconfig ue0 inet "192.168.2.176 netmask 255.255.255.0" > > As we figured out, this means that ifconfig sometimes doesn't set the netmask as we expect it to do: > >> root@csbuild:~ # ifconfig ue0 >> ue0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 >> options=80001<RXCSUM,LINKSTATE> >> ether b8:27:eb:fd:58:69 >> inet 192.168.2.176 netmask 0xffff0000 broadcast 192.168.255.255 >> media: Ethernet autoselect (100baseTX <full-duplex>) >> status: active >> nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> >> root@csbuild:~ # ifconfig ue0 inet "192.168.2.176 netmask 255.0.0.0" >> root@csbuild:~ # echo $? >> 0 >> root@csbuild:~ # ifconfig ue0 >> ue0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 >> options=80001<RXCSUM,LINKSTATE> >> ether b8:27:eb:fd:58:69 >> inet 192.168.2.176 netmask 0xffffff00 broadcast 192.168.2.255 >> media: Ethernet autoselect (100baseTX <full-duplex>) >> status: active >> nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> >> root@csbuild:~ # > > As you can see, ifconfig sets the netmask to 255.255.255.0, ignoring the netmask we provided. If provided with a 10.* address, ifconfig sets the netmask to 255.0.0.0, no matter what actual netmask we entered. Also, it doesn't exit with a status indicating error, which made it a little harder to debug this issue. The following works as expected: > >> root@csbuild:~ # ifconfig ue0 >> ue0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 >> options=80001<RXCSUM,LINKSTATE> >> ether b8:27:eb:fd:58:69 >> inet 192.168.2.176 netmask 0xffffff00 broadcast 192.168.2.255 >> media: Ethernet autoselect (100baseTX <full-duplex>) >> status: active >> nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> >> root@csbuild:~ # ifconfig ue0 inet "192.168.2.176" netmask "255.0.0.0" >> root@csbuild:~ # ifconfig ue0 >> ue0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500 >> options=80001<RXCSUM,LINKSTATE> >> ether b8:27:eb:fd:58:69 >> inet 192.168.2.176 netmask 0xff000000 broadcast 192.255.255.255 >> media: Ethernet autoselect (100baseTX <full-duplex>) >> status: active >> nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL> >> root@csbuild:~ # > What exactly does ifconfig do? It seems to me that it reads the IP address from the quoted string but truncates the netmask. Is this a bug in ifconfig or intended behavior? it's not so much as ifconfig, as the shell you have ifconfig with 3 arguments, the last of which is "192.168.2.176 netmask 255.255.255.0" which ifconfig inspects to see if it has an IP address in it (followed by a space which terminates the test successfully). this is expected behaviour. Though admittedly a less than clear example of it. > > Best wishes > Jeremy > _______________________________________________ > freebsd-net@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >
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