lib: AgentX: use threads instead of eventloop hack
AgentX fd/timeout handling is rather hackishly monkeyed into thread.c.
Replace with code that uses plain thread_* functions.
NB: Net-SNMP's API rivals Quagga's in terms of age and absence of
documentation. netsnmp_check_outstanding_agent_requests() in particular
seems to be unused and is therefore untested.
The most useful documentation on this is actually the blog post Vincent
Bernat wrote when he originally integrated this into lldpd and Quagga:
https://vincent.bernat.im/en/blog/2012-snmp-event-loop.html
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/lib/agentx.c b/lib/agentx.c
index be6b432..5d7d057 100644
--- a/lib/agentx.c
+++ b/lib/agentx.c
@@ -24,11 +24,108 @@
#if defined HAVE_SNMP && defined SNMP_AGENTX
#include <net-snmp/net-snmp-config.h>
#include <net-snmp/net-snmp-includes.h>
+#include <net-snmp/agent/net-snmp-agent-includes.h>
+#include <net-snmp/agent/snmp_vars.h>
#include "command.h"
#include "smux.h"
-int agentx_enabled = 0;
+static int agentx_enabled = 0;
+
+static struct thread_master *agentx_tm;
+static struct thread *timeout_thr = NULL;
+static struct list *events = NULL;
+
+static void agentx_events_update(void);
+
+static int
+agentx_timeout(struct thread *t)
+{
+ timeout_thr = NULL;
+
+ snmp_timeout ();
+ run_alarms ();
+ netsnmp_check_outstanding_agent_requests ();
+ agentx_events_update ();
+ return 0;
+}
+
+static int
+agentx_read(struct thread *t)
+{
+ fd_set fds;
+ struct listnode *ln = THREAD_ARG (t);
+ list_delete_node (events, ln);
+
+ FD_ZERO (&fds);
+ FD_SET (THREAD_FD (t), &fds);
+ snmp_read (&fds);
+
+ netsnmp_check_outstanding_agent_requests ();
+ agentx_events_update ();
+ return 0;
+}
+
+static void
+agentx_events_update(void)
+{
+ int maxfd = 0;
+ int block = 1;
+ struct timeval timeout = { .tv_sec = 0, .tv_usec = 0 };
+ fd_set fds;
+ struct listnode *ln;
+ struct thread *thr;
+ int fd, thr_fd;
+
+ THREAD_OFF (timeout_thr);
+
+ FD_ZERO (&fds);
+ snmp_select_info (&maxfd, &fds, &timeout, &block);
+
+ if (!block)
+ timeout_thr = thread_add_timer_tv (agentx_tm, agentx_timeout, NULL, &timeout);
+
+ ln = listhead (events);
+ thr = ln ? listgetdata (ln) : NULL;
+ thr_fd = thr ? THREAD_FD (thr) : -1;
+
+ /* "two-pointer" / two-list simultaneous iteration
+ * ln/thr/thr_fd point to the next existing event listener to hit while
+ * fd counts to catch up */
+ for (fd = 0; fd < maxfd; fd++)
+ {
+ /* caught up */
+ if (thr_fd == fd)
+ {
+ struct listnode *nextln = listnextnode (ln);
+ if (!FD_ISSET (fd, &fds))
+ {
+ thread_cancel (thr);
+ list_delete_node (events, ln);
+ }
+ ln = nextln;
+ thr = ln ? listgetdata (ln) : NULL;
+ thr_fd = thr ? THREAD_FD (thr) : -1;
+ }
+ /* need listener, but haven't hit one where it would be */
+ else if (FD_ISSET (fd, &fds))
+ {
+ struct listnode *newln;
+ thr = thread_add_read (agentx_tm, agentx_read, NULL, fd);
+ newln = listnode_add_before (events, ln, thr);
+ thr->arg = newln;
+ }
+ }
+
+ /* leftover event listeners at this point have fd > maxfd, delete them */
+ while (ln)
+ {
+ struct listnode *nextln = listnextnode (ln);
+ thread_cancel (listgetdata (ln));
+ list_delete_node (events, ln);
+ ln = nextln;
+ }
+}
/* AgentX node. */
static struct cmd_node agentx_node =
@@ -77,6 +174,8 @@
if (!agentx_enabled)
{
init_snmp("quagga");
+ events = list_new();
+ agentx_events_update ();
agentx_enabled = 1;
return CMD_SUCCESS;
}
@@ -99,6 +198,8 @@
void
smux_init (struct thread_master *tm)
{
+ agentx_tm = tm;
+
netsnmp_enable_subagent ();
snmp_disable_log ();
snmp_enable_calllog ();
@@ -207,6 +308,7 @@
send_v2trap (notification_vars);
snmp_free_varbind (notification_vars);
+ agentx_events_update ();
return 1;
}