Date: Thu, 2 Nov 2006 08:26:27 +0000 From: . <antinvidia@gmail.com> To: freebsd-net@freebsd.org Subject: Reentrant problem with inet_ntoa in the kernel Message-ID: <be0088ce0611020026y4fe07749pd5a984f8744769b@mail.gmail.com>
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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? Thanks MQ
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