[Bugme-new] [Bug 10880] New: include/linux/if_addr.h: negative preferred lifetimes of addresses
bugme-daemon at bugzilla.kernel.org
bugme-daemon at bugzilla.kernel.org
Sat Jun 7 03:04:43 PDT 2008
http://bugzilla.kernel.org/show_bug.cgi?id=10880
Summary: include/linux/if_addr.h: negative preferred lifetimes of
addresses
Product: Networking
Version: 2.5
KernelVersion: 2.6.25.4
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: IPV6
AssignedTo: yoshfuji at linux-ipv6.org
ReportedBy: benedikt at gollatz.net
Recently, I noticed that iproute2 would return me preferred lifetimes of IPv6
adresses close to 2^32 on links where prefixes are advertised with a preferred
lifetime of 0. A quick look into the source revealed that the preferred
lifetime is output using a format string containing "%u"; the incriminating
lines being
struct ifa_cacheinfo *ci = RTA_DATA(rta_tb[IFA_CACHEINFO]);
char buf[128];
fprintf(fp, "%s", _SL_);
[...]
if (ci->ifa_prefered == INFINITY_LIFE_TIME)
sprintf(buf+strlen(buf), " preferred_lft forever");
else
sprintf(buf+strlen(buf), " preferred_lft %usec",
ci->ifa_prefered);
fprintf(fp, " %s", buf);
When calling iproute2 oftenly shortly after a prefix has been advertised on the
link, one could see that there actually was an integer underflow going on (the
output changed from "0" to "forever" to 2^32-1).
Interestringly, if_addr.h does define ifa_prefered to be a __u32, so iproute2
merely implements the interface. RFC4862 mandates that the preferred lifetime
always is lower than or equal to the valid lifetime, which is also defined to
be a __u32.
I'm certainly no expert in the linux kernel code, but this looks like a bug to
me. Why is ifa_prefered defined to be non-negative?
Benedikt
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