<h3>Description</h3>

<p>When registering a soft client running on my Android phone (Grandstream Wave), Kamailio crashes every time when the client registers. When setting the debug level below 3 Kamailio does not crash. I have only found the problem with this SIP client. Others are working fine.</p>
<h3>Troubleshooting</h3>
<h4>Reproduction</h4>

<p>Set debug level greather than 2 and register the Grandstream Wave soft client from an Android phone. Kamailio then crashes.</p>
<h4>Log Messages</h4>

<p>just before crashing I get the following message:<br>
0(7819) ERROR:  [core/udp_server.c:484]: udp_rcv_loop(): print buffer building failed (10/16/4)</p>
<h3>Possible Solutions</h3>

<p>The problem seems to come from non-printable characters sent by the SIP client causing Kamailio to crash.</p>
<p>Changing line 482 in udp_server.c from<br>
l = snprintf(printbuf+j, 6, " %02X ", buf[i]);<br>
to<br>
l = snprintf(printbuf+j, 6, " %02X ", (unsigned char)buf[i]);</p>
<p>fixes the problem.</p>
<p>The compiler treats buf[i] as a signed integer and prepends 'FFFFFF' to the string making it longer than 6 characters. Casting buf[i] as an unsigned char prevents Kamailio from crashing.</p>
<h3>Additional Information</h3>
<ul>
<li><strong>Kamailio Version</strong> - output of <code>kamailio -v</code></li>
</ul>
<p>version: kamailio 5.1.0 (x86_64/linux)<br>
flags: STATS: Off, USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MEM, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES<br>
ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE 262144, MAX_LISTEN 16, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB<br>
poll method support: poll, epoll_lt, epoll_et, sigio_rt, select.<br>
id: unknown<br>
compiled with gcc 5.3.1</p>
<ul>
<li><strong>Operating System</strong>:</li>
</ul>

<p>Ubuntu 16.04 (Xenial)</p>

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