lock up in recvfrom()

Hi,
 
I'm using net-snmp-5.2.1.2, RH Enterprise Edition.
 
When sending traps with the configuration:
trapsess -v2c -Ci -cCCCC -r5 -t1 UDP:192.168.xx.yy:162
trap2sink  localhost
 
with snmptrapd running on both machines (local host, and 192.168.xx.yy),
 
I've encountered the a lock up in recvfrom() function :
 
#0  0x00fbddae in recvfrom () from /lib/tls/libpthread.so.0
#1  0x0016132e in netsnmp_udp_recv (t=0x85efc00, buf=0xaeea1d88,
size=65536,
#2  0x001436d7 in _sess_read (sessp=0x860e9c0, fdset=0x861e5d0)
#3  0x00144480 in snmp_sess_read (sessp=0x860e9c0, fdset=0xaedfef60)
#4  0x0014349a in snmp_read (fdset=0xaedfef60) at snmp_api.c:5260
#5  0x0011fff0 in snmp_synch_response_cb (ss=0x861e5d0, pdu=0xaedfef60,
#6  0x001200ce in snmp_synch_response (ss=0x861e5d0, pdu=0xaeea0268,
#7  0x002ac438 in send_trap_to_sess (sess=0x861e5d0,
template_pdu=0xaee92118)
#8  0x00b81b8f in send_notifications (major=1, minor=7,
serverarg=0xaee92118,
#9  0x0015c325 in snmp_call_callbacks (major=1, minor=7,
caller_arg=0xaee92118)
#10 0x002ac056 in netsnmp_send_traps (trap=-1, specific=-1,
#11 0x002ac377 in send_enterprise_trap_vars (trap=-1, specific=-1,
#12 0x002ac502 in send_trap_vars (trap=1578772, specific=-1361056608,
 
I've take a look in snmpUDPDomain.c, netsnmp_udp_recv() and I've made
the following small change:
-  rc = recvfrom(t->sock, buf, size, 0, from, &fromlen);
+ rc = recvfrom(t->sock, buf, size, MSG_DONTWAIT, from, &fromlen);
 
This patch was working well for awhile but after ~5 hours (with ~2-3
traps /sec, with 1 and 11 varbinds) I received a core dump.
 
Using host libthread_db library "/lib/tls/libthread_db.so.1".
Core was generated by `/blue/usr/local/snmp/sbin/snmpd -f -Lf
/blue/var/log/snmpd.log'.
Program terminated with signal 11, Segmentation fault.
#0  0x003b063d in netsnmp_udp_send (t=0x9e321f8, buf=0x1cbd8f39,
size=583, opaque=0x6c, olength=0x6c) at snmpUDPDomain.c:158
158                  if (opaque != NULL && *opaque != NULL &&
 
#1  0x00393d45 in snmp_resend_request (slp=0x6c, rp=0xa6371c10,
incr_retries=1) at snmp_api.c:5949
        isp = (struct snmp_internal_session *) 0x1cbd8f39
        sp = (netsnmp_session *) 0x9e5f2f0
        transport = (netsnmp_transport *) 0x9e321f8
        pktbuf = (u_char *) 0x1cbd8980 "224t224t\001"
        packet = (u_char *) 0x1cbd8f39
"0\202\002C\002\001\001\004\006public202\0024\002\004!_\002\001"
        pktbuf_len = 2048
        offset = 583
        length = 583
        tv = {tv_sec = 0, tv_usec = 482185017}
        now = {tv_sec = 3, tv_usec = 165878668}
        result = 0
#2  0x003941d4 in snmp_sess_timeout (sessp=0x9e48710) at snmp_api.c:6058
        sp = (netsnmp_session *) 0x9e5f2f0
        isp = (struct snmp_internal_session *) 0x9e3cb68
        rp = (netsnmp_request_list *) 0xa6371c10
        orp = (netsnmp_request_list *) 0x0
        freeme = (netsnmp_request_list *) 0x0
        now = {tv_sec = 1140752367, tv_usec = 376573}
        callback = 0x70
        magic = (void *) 0x6c
        sptr = (struct snmp_secmod_def *) 0x6c
#3  0x00393c05 in snmp_timeout () at snmp_api.c:5851
        slp = (struct session_list *) 0x9e48710
#4  0x08050ac5 in receive () at snmpd.c:1185
        numfds = 11
        readfds = {__fds_bits = {0 <repeats 32 times>}}
        writefds = {__fds_bits = {0 <repeats 32 times>}}
        exceptfds = {__fds_bits = {0 <repeats 32 times>}}
        timeout = {tv_sec = 0, tv_usec = 0}
        tvp = (struct timeval *) 0xbfff5ee8
        count = 0
        block = 0
        i = 0
#5  0x08050122 in main (argc=4, argv=0xbfff7204) at snmpd.c:993
        c = 0xb7f8a6
"\205211N\213030215\215(213U\b\211\017\211\024$225\034213u213\215\030213
213\225 2111a"
        astring = 0x0
        options = "aAc:CdD::fhHI:l:L:m:M:p:P:qrsS:UvV-:g:u:x:X", '\0'
<repeats 84 times>
        arg = 108
        i = 134889333
        ret = 64
        dont_fork = 1
        dont_zero_log = 0
        syslog_log = 0
        uid = 0
        gid = 0
        agent_mode = -1
        logfile = "/blue/var/log", '\0' <repeats 4083 times>
        cptr = 0x0
        argvptr = (char **) 0x9dd8d78
        pid_file = 0x0
        option_compatability = "-Le"
        fd = 134889333
        PID = (FILE *) 0x0
 
 
I guess my patch generated this crash since "opaque" is set in
netsnmp_udp_recv() that I've modified.
 
At that point I would need some help.
 
Thanks a lot,
Eugen