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sysctl(NET_RT_IFLIST) up to several (currently 5) times.

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This will make the behavior robuster if many addresses are added
after the size estimation of storage at the first sysctl.

Reviewed by:	JINMEI Tatuya <jinmei@isl.rdc.toshiba.co.jp>
MFC after:	1 week
This commit is contained in:
ume 2002-07-25 08:08:30 +00:00
parent 60d8f7e6de
commit f898a0ffb1
1 changed files with 29 additions and 8 deletions
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37
lib/libc/net/getifaddrs.c
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@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
#include <net/if_dl.h>
#endif
#include <errno.h>
#include <ifaddrs.h>
#include <stdlib.h>
#include <string.h>
@ -84,6 +85,8 @@ __FBSDID("$FreeBSD$");
#define HAVE_IFM_DATA
#endif
#define MAX_SYSCTL_TRY 5
int
getifaddrs(struct ifaddrs **pif)
{
@ -91,6 +94,7 @@ getifaddrs(struct ifaddrs **pif)
int dcnt = 0;
int ncnt = 0;
#ifdef NET_RT_IFLIST
int ntry = 0;
int mib[6];
size_t needed;
char *buf;
@ -123,14 +127,31 @@ getifaddrs(struct ifaddrs **pif)
mib[3] = 0; /* wildcard address family */
mib[4] = NET_RT_IFLIST;
mib[5] = 0; /* no flags */
if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
return (-1);
if ((buf = malloc(needed)) == NULL)
return (-1);
if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
free(buf);
return (-1);
}
do {
/*
* We'll try to get addresses several times in case that
* the number of addresses is unexpectedly increased during
* the two sysctl calls. This should rarely happen, but we'll
* try to do our best for applications that assume success of
* this library (which should usually be the case).
* Portability note: since FreeBSD does not add margin of
* memory at the first sysctl, the possibility of failure on
* the second sysctl call is a bit higher.
*/
if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
return (-1);
if ((buf = malloc(needed)) == NULL)
return (-1);
if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
if (errno != ENOMEM || ++ntry >= MAX_SYSCTL_TRY) {
free(buf);
return (-1);
}
free(buf);
buf = NULL;
}
} while (buf == NULL);
for (next = buf; next < buf + needed; next += rtm->rtm_msglen) {
rtm = (struct rt_msghdr *)(void *)next;