Author: eugen
Date: Sat Aug 18 10:58:44 2018
New Revision: 338013
URL: https://svnweb.freebsd.org/changeset/base/338013
Log:
bsnmpd(8): fix and optimize interface description processing
* correctly prepare a buffer to obtain interface description from a kernel and
truncate long description instead of dropping it altogether and
spamming logs;
* skip calling strlen() for each description and each SNMP request
for MIB-II/ifXTable's ifAlias.
* teach bsnmpd to allocate memory dynamically for interface descriptions
to decrease memory usage for common case and not to break
if long description occurs;
PR: 217763
Reviewed by: harti and others
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D16459
Modified:
head/contrib/bsnmp/snmp_mibII/mibII.c
head/contrib/bsnmp/snmp_mibII/mibII.h
head/contrib/bsnmp/snmp_mibII/mibII_interfaces.c
head/contrib/bsnmp/snmp_mibII/snmp_mibII.h
Modified: head/contrib/bsnmp/snmp_mibII/mibII.c
==============================================================================
--- head/contrib/bsnmp/snmp_mibII/mibII.c Sat Aug 18 10:14:02 2018
(r338012)
+++ head/contrib/bsnmp/snmp_mibII/mibII.c Sat Aug 18 10:58:44 2018
(r338013)
@@ -439,11 +439,15 @@ mibif_restart_mibII_poll_timer(void)
int
mib_fetch_ifmib(struct mibif *ifp)
{
+ static int kmib[2] = { -1, 0 }; /* for sysctl net.ifdescr_maxlen */
+
int name[6];
+ size_t kmiblen = nitems(kmib);
size_t len;
void *newmib;
struct ifmibdata oldmib = ifp->mib;
struct ifreq irr;
+ unsigned int alias_maxlen = MIBIF_ALIAS_SIZE_MAX;
if (fetch_generic_mib(ifp, &oldmib) == -1)
return (-1);
@@ -515,18 +519,69 @@ mib_fetch_ifmib(struct mibif *ifp)
}
out:
+
+ /*
+ * Find sysctl mib for net.ifdescr_maxlen (one time).
+ * kmib[0] == -1 at first call to mib_fetch_ifmib().
+ * Then kmib[0] > 0 if we found sysctl mib for net.ifdescr_maxlen.
+ * Else, kmib[0] == 0 (unexpected error from a kernel).
+ */
+ if (kmib[0] < 0 &&
+ sysctlnametomib("net.ifdescr_maxlen", kmib, &kmiblen) < 0) {
+ kmib[0] = 0;
+ syslog(LOG_WARNING, "sysctlnametomib net.ifdescr_maxlen: %m");
+ }
+
+ /*
+ * Fetch net.ifdescr_maxlen value every time to catch up with changes.
+ */
+ len = sizeof(alias_maxlen);
+ if (kmib[0] > 0 && sysctl(kmib, 2, &alias_maxlen, &len, NULL, 0) < 0) {
+ /* unexpected error from the kernel, use default value */
+ alias_maxlen = MIBIF_ALIAS_SIZE_MAX;
+ syslog(LOG_WARNING, "sysctl net.ifdescr_maxlen: %m");
+ }
+
+ /*
+ * Kernel limit might be decreased after interfaces got
+ * their descriptions assigned. Try to obtain them anyway.
+ */
+ if (alias_maxlen == 0)
+ alias_maxlen = MIBIF_ALIAS_SIZE_MAX;
+
+ /*
+ * Allocate maximum memory for a buffer and later reallocate
+ * to free extra memory.
+ */
+ if ((ifp->alias = malloc(alias_maxlen)) == NULL) {
+ syslog(LOG_WARNING, "malloc(%d) failed: %m", (int)alias_maxlen);
+ goto fin;
+ }
+
strlcpy(irr.ifr_name, ifp->name, sizeof(irr.ifr_name));
- irr.ifr_buffer.buffer = MIBIF_PRIV(ifp)->alias;
- irr.ifr_buffer.length = sizeof(MIBIF_PRIV(ifp)->alias);
+ irr.ifr_buffer.buffer = ifp->alias;
+ irr.ifr_buffer.length = alias_maxlen;
if (ioctl(mib_netsock, SIOCGIFDESCR, &irr) == -1) {
- MIBIF_PRIV(ifp)->alias[0] = 0;
+ free(ifp->alias);
+ ifp->alias = NULL;
if (errno != ENOMSG)
syslog(LOG_WARNING, "SIOCGIFDESCR (%s): %m", ifp->name);
} else if (irr.ifr_buffer.buffer == NULL) {
- MIBIF_PRIV(ifp)->alias[0] = 0;
+ free(ifp->alias);
+ ifp->alias = NULL;
syslog(LOG_WARNING, "SIOCGIFDESCR (%s): too long (%zu)",
ifp->name, irr.ifr_buffer.length);
+ } else {
+ ifp->alias_size = strnlen(ifp->alias, alias_maxlen) + 1;
+
+ if (ifp->alias_size > MIBIF_ALIAS_SIZE)
+ ifp->alias_size = MIBIF_ALIAS_SIZE;
+
+ if (ifp->alias_size < alias_maxlen)
+ ifp->alias = realloc(ifp->alias, ifp->alias_size);
}
+
+fin:
ifp->mibtick = get_ticks();
return (0);
}
@@ -706,6 +761,10 @@ mibif_free(struct mibif *ifp)
mibif_reset_hc_timer();
}
+ if (ifp->alias != NULL) {
+ free(ifp->alias);
+ ifp->alias = NULL;
+ }
free(ifp->private);
ifp->private = NULL;
free(ifp->physaddr);
Modified: head/contrib/bsnmp/snmp_mibII/mibII.h
==============================================================================
--- head/contrib/bsnmp/snmp_mibII/mibII.h Sat Aug 18 10:14:02 2018
(r338012)
+++ head/contrib/bsnmp/snmp_mibII/mibII.h Sat Aug 18 10:58:44 2018
(r338013)
@@ -57,8 +57,9 @@
#include "snmp_mibII.h"
#include "mibII_tree.h"
-/* maximum size of the interface alias */
+/* maximum size of the interface alias unless overridden with
net.ifdescr_maxlen */
#define MIBIF_ALIAS_SIZE (64 + 1)
+#define MIBIF_ALIAS_SIZE_MAX 1024
/*
* Interface list and flags.
@@ -81,8 +82,6 @@ struct mibif_private {
uint64_t hc_imcasts;
uint64_t hc_ipackets;
- /* this should be made public */
- char alias[MIBIF_ALIAS_SIZE];
};
#define MIBIF_PRIV(IFP) ((struct mibif_private *)((IFP)->private))
Modified: head/contrib/bsnmp/snmp_mibII/mibII_interfaces.c
==============================================================================
--- head/contrib/bsnmp/snmp_mibII/mibII_interfaces.c Sat Aug 18 10:14:02
2018 (r338012)
+++ head/contrib/bsnmp/snmp_mibII/mibII_interfaces.c Sat Aug 18 10:58:44
2018 (r338013)
@@ -528,7 +528,7 @@ op_ifxtable(struct snmp_context *ctx, struct snmp_valu
break;
case LEAF_ifAlias:
- ret = string_get(value, MIBIF_PRIV(ifp)->alias, -1);
+ ret = string_get(value, ifp->alias, ifp->alias_size - 1);
break;
case LEAF_ifCounterDiscontinuityTime:
Modified: head/contrib/bsnmp/snmp_mibII/snmp_mibII.h
==============================================================================
--- head/contrib/bsnmp/snmp_mibII/snmp_mibII.h Sat Aug 18 10:14:02 2018
(r338012)
+++ head/contrib/bsnmp/snmp_mibII/snmp_mibII.h Sat Aug 18 10:58:44 2018
(r338013)
@@ -80,6 +80,9 @@ struct mibif {
/* to be set by ifType specific modules. This is ifSpecific. */
struct asn_oid spec_oid;
+ char *alias;
+ size_t alias_size;
+
/* private data - don't touch */
void *private;
};
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