scp of sysfs file repeats data

[Matt Johnston]

I see what you mean. I'll update scp to OpenSSH's latest -
there are a few changes to be merged.

Cheers,
Matt

On Tue, Jun 23, 2015 at 09:11:35AM +0200, Peter Korsgaard wrote:
> >>>>> "Craig" == Craig McQueen <craig.mcqueen at innerrange.com> writes:
> 
>  > I tried doing scp of a sysfs attribute. I found that it duplicated the
>  > data, as well as adding extra NUL bytes. E.g.:
> 
>  > # scp /sys/class/net/eth0/address localhost:
>  > # cat ~/address
>  > d0:39:72:53:ef:0e
>  > d0:39:72:53:ef:0e
>  > # hexdump -C ~/address
>  > 00000000  64 30 3a 33 39 3a 37 32  3a 35 33 3a 65 66 3a 30  |d0:39:72:53:ef:0|
>  > 00000010  65 0a 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |e...............|
>  > 00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
>  > *
>  > 00000800  64 30 3a 33 39 3a 37 32  3a 35 33 3a 65 66 3a 30  |d0:39:72:53:ef:0|
>  > 00000810  65 0a 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |e...............|
>  > 00000820  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
>  > *
>  > 00001000
> 
>  > Does that seem normal?
> 
> No, that looks like a bug. I see it as well here:
> 
> strace output looks like this (for a sysfs property called control).
> 
> open("control", O_RDONLY|O_LARGEFILE)   = 3
> fstat64(3, {st_mode=S_IFREG|0644, st_size=4096, ...}) = 0
> write(6, "C0644 4096 control\n", 19)    = 19
> read(3, "auto\n", 2048)                 = 5
> read(3, "", 2043)                       = 0
> write(6, "auto\n\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2048) = 2048
> read(3, "", 2048)                       = 0
> write(6, "auto\n\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 2048) = 2048
> 
> The logic in scp.c always tries to copy st_size bytes, but the sysfs
> properties always claim to be 4096 while they in reality are shorter.
> 
> I guess the loop in source() needs to be changed to end on error or eof
> instead.
> 
> -- 
> Bye, Peter Korsgaard