Dfyjkt

I'm having some issues with SO_PRIORITY, when used with setsockopt().

My doubt is about the WME MAC layer queues and socket priority when sending packets (defing, among other things, the AIFS times, in place of DIFS). I'm able to set a certain priority with:
setsockopt(sFd,SOL_SOCKET,SO_PRIORITY,&up,sizeof(up))
where "up" is the desired user priority (for instance, up=4 to use the AC_VO queue).
This seems to work both with raw and IP datagram sockets.

The problem is that the MAC queues are correctly used only when sending unicast packets (which are actually acknowledged); when sending broadcast (or multicast) data, as I'm required to do, only the "AC_BE" (up=0) queue is used, no matter what I set with SO_PRIORITY.

Do you know why? I actually want to properly use these queues also for broadcast transmissions, as it may be very useful for a research work I'm doing.

This is part of the code I'm using to send the packets out (here a raw socket is used, but the same happens with non-raw sockets, as AF_INET datagram ones):

// Open socket
sFd=socket(AF_PACKET,SOCK_RAW,htons(ETH_P_ALL));
if(sFd==-1) 
 perror("socket() error");
 exit(EXIT_FAILURE);


// Getting WLAN interface index using a custom library (wlanLookup() and macAddrTypeGet() functions
ret_wlanl_val=wlanLookup(devname,&ifindex,srcmacaddr,0);
if(ret_wlanl_val<=0) 
 fprintf(stderr,"wlanLookup() error.n");
 rs_printerror(stderr,ret_wlanl_val);
 close(sFd);
 exit(EXIT_FAILURE);


if(macAddrTypeGet(srcmacaddr)==MAC_BROADCAST) 
 fprintf(stderr,"Could not retrieve source MAC address.n");
 close(sFd);
 exit(EXIT_FAILURE);


// Prepare sockaddr_ll structure
bzero(&addrll,sizeof(addrll));
addrll.sll_ifindex=ifindex;
addrll.sll_family=AF_PACKET;
addrll.sll_protocol=htons(ETH_P_ALL);

// Bind to the wireless interface
if(bind(sFd,(struct sockaddr *) &addrll,sizeof(addrll))<0) 
 perror("Cannot bind to interface: bind() error");
 close(sFd);
 exit(EXIT_FAILURE);


// Print AC corresponding to selected UP (and handle possible wrong UP)
up=atoi(argv[3]);
switch(up) 
 case 0:
 case 3:
 fprintf(stdout,"AC_BE is selected, with UP: %d.n",up);
 break;

 case 1:
 case 2:
 fprintf(stdout,"AC_BK is selected, with UP: %d.n",up);
 break;

 case 4:
 case 5:
 fprintf(stdout,"AC_VI is selected, with UP: %d.n",up);
 break;

 case 6:
 case 7:
 fprintf(stdout,"AC_VO is selected, with UP: %d.n",up);
 break;

 default:
 fprintf(stderr,"Wrong UP specified. AC_BE will be used.n");
 up=0;
 break;


// Set user priority using socket layer options (does not work with broadcast?)
if(setsockopt(sFd,SOL_SOCKET,SO_PRIORITY,&up,sizeof(up))!=0) 
 perror("setsockopt() for SO_PRIORITY error");
 close(sFd);
 exit(EXIT_FAILURE);


// Set broadcast permission using socket layer options (is this really required?)
if(setsockopt(sFd,SOL_SOCKET,SO_BROADCAST,(void *) &broadPerm,sizeof(broadPerm))!=0) 
 perror("setsockopt() for SO_BROADCAST error");
 close(sFd);
 exit(EXIT_FAILURE);


//... Prepare payload, headers and timer to periodically send data...

while(1) 
 // poll waiting for events happening on the timer descriptor (i.e. wait for timer expiration)
 if(poll(&timerMon,1,INDEFINITE_BLOCK)>0) 
 // "Clear the event" by performing a read() on a junk variable
 read(clockFd,&junk,sizeof(junk));
 // Send brodcast data (if verbose==1, print '.' for each sent datagram)
 // Prepare datagram

 // ... Prepare datagram to be sent (contained in "ethernetpacket", with size "finalpktsize")

 if(sendto(sFd,ethernetpacket,finalpktsize,0,(struct sockaddr *)&addrll,sizeof(struct sockaddr_ll))!=finalpktsize) 
 perror("sendto() for sending broadcasted data failed");
 fprintf(stderr,"The program will be terminated now");
 break;
 

 if(verbose) 
 fprintf(stdout,".");
 fflush(stdout);
 
 


//... free variables, close socket, ...

Thank you very much in advance.