Date: Thu, 2 Nov 2006 08:25:43 -0600 From: Brooks Davis <brooks@one-eyed-alien.net> To: "." <antinvidia@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: Reentrant problem with inet_ntoa in the kernel Message-ID: <20061102142543.GC70915@lor.one-eyed-alien.net> In-Reply-To: <be0088ce0611020026y4fe07749pd5a984f8744769b@mail.gmail.com> References: <be0088ce0611020026y4fe07749pd5a984f8744769b@mail.gmail.com>
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[-- Attachment #1 --] On Thu, Nov 02, 2006 at 08:26:27AM +0000, . wrote: > Hi, > > I am confused by the use of inet_ntoa function in the kernel. > > The function inet_ntoa in the /sys/libkern/inet_ntoa.c uses a static array > static char buf[4 * sizeof "123"]; > to store the result. And it returns the address of the array to the caller. > > I think this inet_ntoa is not reentrant, though there are several functions > calling it. If two functions call it simultaneously, the result will be > corrupted. Though I haven't really encountered this situation, it may occur > someday, especially when using multi-processors. > > There is another reentrant version of inet_ntoa called inet_ntoa_r in the > same file. It has been there for several years, but just used by ipfw2 for > about four times in 7-CURRENT. In my patch, I replaced all the calls to > inet_ntoa with calls to inet_ntoa_r. > > By the way, some of the original calls is written in this style: > strcpy(buf, inet_ntoa(ip)) > The modified code is written in this style > inet_ntoa_r(ip, buf) > This change avoids a call to strcpy, and can save a little time. > > Here is the patch. > http://people.freebsd.org/~delphij/misc/patch-itoa-by-nodummy-at-yeah-net > > I've already sent to PR(kern/104738), but got no reply, maybe it should be > discussed here first? I've got to agree with other posters that the stack variable allocations are ugly. What about extending log and printf to understand ip4v addresses? That's 90% of the uses and the others appears to have buffers already. -- Brooks [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) iD8DBQFFSf/mXY6L6fI4GtQRAq3/AKCzT92xeif23vFSDc2k1b3ZpFdolACgx8n6 da2TOJtPJpXc2Q3N9Ih7Ju0= =GyRC -----END PGP SIGNATURE-----
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