Date: Sun, 28 Apr 2024 21:33:45 +0200 From: Dirk-Willem van Gulik <dirkx@webweaving.org> To: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Multicast & Tunnel devices Message-ID: <D00CB346-F704-4111-8C7B-648EFA8A8C89@webweaving.org>
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[-- Attachment #1 --]
Would anyone know if there is something special with tunnel devices and multicast ?
I’ve got some code that happily processes multicast packets on a normal interface; but appears not to do this on a tunnel interface. Tun0 shows multicast enabled:
tun0: flags=8043<UP,BROADCAST,RUNNING,MULTICAST> metric 0 mtu 1500
Tcpdump on that interface gives the expected thing (here with mDNS):
tcpdump -n -i tun0 port 5353
listening on tun0, link-type NULL (BSD loopback), capture size 262144 bytes
19:26:03.976259 IP 10.31.0.6.5353 > 224.0.0.251.5353: 0 PTR (QM)? _raop._tcp.local. (34)
And code, with a simple IP_ADD_MEMBERSHIP of the MC group on the IP of the local interface below works on a normal interface (e.g. igb0/10.0.0.1/24).
./listener 10.0.0.1 224.0.0.251 5353
Received packet, len=128
etc
But yields no output if ran against above tun0 interface (while tcpdump on same is fine). Does that ring a bell with anyone ?
Dw
int main(int argc, char *argv[])
{
struct sockaddr_in addr;
struct ip_mreq mreq;
// skip error trapping command line arguments
char* ip = argv[1];
char* group = argv[2];
int port = atoi(argv[3]); // 0 if error, which is an invalid port
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(port);
mreq.imr_interface.s_addr = inet_addr(ip);
mreq.imr_multiaddr.s_addr = inet_addr(group);
// skip error trapping on inet_addr
int fd = socket(AF_INET, SOCK_DGRAM, 0);
// skip error trapping socket
if (bind(fd, (struct sockaddr*) &addr, sizeof(addr)) < 0) {
// skip error trapping
if (setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char*) &mreq, sizeof(mreq)) < 0 ){
// skip error trapping argumetns
while (1) {
..
int nbytes = recvfrom(fd,msgbuf,MSGBUFSIZE,0,(struct sockaddr *) &addr,&addrlen);
if (nbytes < 0) {
perror("recvfrom");
return 1;
}
printf(“Received packet, len=%d\n", nbytes);
}
[-- Attachment #2 --]
<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">Would anyone know if there is something special with tunnel devices and multicast ? <div><br></div><div>I’ve got some code that happily processes multicast packets on a normal interface; but appears not to do this on a tunnel interface. Tun0 shows multicast enabled:<div><span class="Apple-tab-span" style="white-space:pre"> </span></div><div><span class="Apple-tab-span" style="white-space:pre"> </span><span style="font-family: Menlo; font-size: 11px;">tun0: flags=8043<UP,BROADCAST,RUNNING,MULTICAST> metric 0 mtu 1500</span></div><div><span style="font-family: Menlo; font-size: 11px;"><br></span></div><div><font face="Menlo"><span style="font-size: 11px;">Tcpdump on that interface gives the expected thing (here with mDNS):</span></font></div><div><font face="Menlo"><span style="font-size: 11px;"><br></span></font></div><div><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"><span class="Apple-tab-span" style="white-space:pre"> </span>tcpdump -n -i tun0 port 5353</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span class="Apple-tab-span" style="white-space:pre"> </span>listening on tun0, link-type NULL (BSD loopback), capture size 262144 bytes</p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"><span class="Apple-tab-span" style="white-space:pre"> </span>19:26:03.976259 IP 10.31.0.6.5353 > 224.0.0.251.5353: 0 PTR (QM)? _raop._tcp.local. (34)</span></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"><br></span></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures">And code, with a simple </span>IP_ADD_MEMBERSHIP of the MC group on the IP of the local interface below works on a normal interface (e.g. igb0/10.0.0.1/24). </p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"><br></span></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"><span class="Apple-tab-span" style="white-space:pre"> </span>./listener </span>10.0.0.1 224.0.0.251 5353</p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span class="Apple-tab-span" style="white-space:pre"> </span>Received packet, len=128</p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span class="Apple-tab-span" style="white-space:pre"> </span>etc</p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><br></p><p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures;">But yields no output if ran against above tun0 interface (while tcpdump on same is fine). Does that ring a bell with anyone ?</span></p><p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures;"><br></span></p><p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures;">Dw</span></p></div><div><span style="font-variant-ligatures: no-common-ligatures;"><br></span></div><div><span style="font-variant-ligatures: no-common-ligatures;"><br></span></div><div><span style="font-variant-ligatures: no-common-ligatures;"><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures">int main(int argc, char *argv[])</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures">{</span></p><p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"> struct sockaddr_in addr;</p><p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures;"> struct ip_mreq mreq;</span></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><br></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span class="Apple-tab-span" style="white-space: pre;"> </span>// skip error trapping command line arguments</p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><br></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"> char* ip = argv[1]; </p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> char* group = argv[2]; </span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> int port = atoi(argv[3]); // 0 if error, which is an invalid port</span></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><br></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> memset(&addr, 0, sizeof(addr));</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> addr.sin_family = AF_INET;</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> addr.sin_addr.s_addr = htonl(INADDR_ANY);</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> addr.sin_port = htons(port);</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal; min-height: 13px;"><span style="font-variant-ligatures: no-common-ligatures"></span><br></p>
<p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures;"> mreq.imr_interface.s_addr = inet_addr(ip); </span></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"> mreq.imr_multiaddr.s_addr = inet_addr(group);</p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><br></p><p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span class="Apple-tab-span" style="white-space:pre"> </span>// skip error trapping on inet_addr</p><div><br></div><p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures;"> int fd = socket(AF_INET, SOCK_DGRAM, 0);</span></p><p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span class="Apple-tab-span" style="white-space: pre;"> </span>// skip error trapping socket</p><div><br></div>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> if (bind(fd, (struct sockaddr*) &addr, sizeof(addr)) < 0) {</span></p>
<p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span class="Apple-tab-span" style="white-space: pre;"> </span>// skip error trapping</p><div><br></div>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> if (</span>setsockopt(<span style="font-variant-ligatures: no-common-ligatures;">fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char*) &mreq, sizeof(mreq)</span>) < 0 ){</p>
<p style="margin: 0px; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span class="Apple-tab-span" style="white-space: pre;"> </span>// skip error trapping argumetns</p><div><br></div>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> while (1) {</span></p><p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"><span class="Apple-tab-span" style="white-space:pre"> </span>..</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"> int nbytes = recvfrom(fd,msgbuf,MSGBUFSIZE,0,(struct sockaddr *) &addr,&addrlen);</p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> if (nbytes < 0) {</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> perror("recvfrom");</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> return 1;</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"> }</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"><span style="font-variant-ligatures: no-common-ligatures"><span class="Apple-tab-span" style="white-space:pre"> </span>printf(“Received packet, len=%d\n", nbytes);</span></p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;"> }</p>
<p style="margin: 0px; font-style: normal; font-variant-caps: normal; font-stretch: normal; font-size: 11px; line-height: normal; font-family: Menlo; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-variant-emoji: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal; min-height: 13px;"><br></p></span></div></div></body></html>
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