[Dnsmasq-discuss] Announce: dnsmasq-2.73rc1

[Simon Kelley]

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Hmm, from the BUGS section of the manpage for realpath:

The POSIX.1-2001 standard version of this function is broken by design,
since it is impossible to determine a suitable size for the output buf?
fer,  resolved_path.   According  to  POSIX.1-2001  a  buffer  of  size
PATH_MAX suffices, but PATH_MAX need not be a defined constant, and may
have to be obtained using pathconf(3).  And asking pathconf(3) does not
really  help,  since,  on  the  one hand POSIX warns that the result of
pathconf(3) may be huge and unsuitable for mallocing memory, and on the
other  hand  pathconf(3)  may return -1 to signify that PATH_MAX is not
bounded.   The  resolved_path == NULL  feature,  not  standardized   in
POSIX.1-2001,  but  standardized  in  POSIX.1-2008,  allows this design
problem to be avoided.


It looks like your C library has the impossible-to-use-safely
POSIX-2001 version, and changing the dnsmasq code to accomodate that
cannot be safe. I think the best solution to this is to recommend
building dnsmasq with

make COPTS=-DNO_INOTIFY

in this case. It will still work fine using the polling method which
has worked for 15 years.


Cheers,

Simon.




On 20/03/15 12:49, Alfonso Ranieri wrote:
> Il 20/03/2015 00:42, Simon Kelley ha scritto:
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>> I want to start the release-process towards 2.73. There's a whole
>> heap of good stuff since 2.72, and good reasons to get it out
>> there before proceeding further with stuff that's in progress.
>> 
>> Please test if you can, code is available at
> 
> I, am using dnsmasq in a small router firmware for some Netgear
> router modem.
> 
> To make the new inotify system dnsmasq compile under my toolchain
> (which is gcc 4.2.2, kernel 2.6.30, uClibc 0.9.29) I had to make
> these changes (expecially realpath() wants the second args to be
> not NULL)
> 
> --- src/inotify.c.orig  2015-03-20 13:44:29.000000000 +0100 +++
> src/inotify.c       2015-03-20 13:44:42.000000000 +0100 @@ -19,6
> +19,13 @@
> 
> #include <sys/inotify.h>
> 
> +#ifndef IN_CLOEXEC +#ifndef O_CLOEXEC +#define O_CLOEXEC 02000000 
> +#endif +#define IN_CLOEXEC O_CLOEXEC +#endif + #ifndef
> IN_NONBLOCK # define IN_NONBLOCK O_NONBLOCK #endif @@ -57,7 +64,9
> @@ for (res = daemon->resolv_files; res; res = res->next) { char *d
> = NULL, *path; -      if (!(path = realpath(res->name, NULL))) +
> char _b[256]; + +      if (!(path = realpath(res->name, _b))) { /*
> realpath will fail if the file doesn't exist, but dnsmasq copes
> with missing files, so fall back
> 
> Ciao. Alfonso
> 
> _______________________________________________ Dnsmasq-discuss
> mailing list Dnsmasq-discuss at lists.thekelleys.org.uk 
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> 

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