Re: [PATCH 0/2] AF_PACKET fanout support

Dave,

Thanks for these patches!  Is it possible you could use an alternative
term than "fanout"?  I think this may be more often associated with a
transmit operation (e.g. multicast fanout).

Also, another useful mode of steering would be to steer packets to a
socket which was recently processed by a thread running on the same
CPU; somewhat analogous to RFS (cc'ed WIllem Bruijn who is already
working on this I believe).

Tom

On Mon, Jul 4, 2011 at 9:20 PM, David Miller [off-list ref] wrote:

This is a fully functional version, I've tested both hash and
load-balance modes successfully.  I plan to commit this to
net-next-2.6 very soon.

Below is a test program that other people can play with
if they want.  It basically creates 4 threads, and creates
an AF_PACKET fanout amongst them.  Each thread prints out
it's pid in parentheses every time it receives 10 packets.
After each thread processes 10,000 packets, it exits.

Try things like "./test eth0 hash", "./test eth0 lb", etc.

Signed-off-by: David S. Miller <davem@davemloft.net>

--------------------
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <sys/types.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/ioctl.h>

#include <unistd.h>

#include <linux/if_ether.h>
#include <linux/if_packet.h>

#include <net/if.h>

static const char *device_name;
static int fanout_type;
static int fanout_id;

#ifndef PACKET_FANOUT
#define PACKET_FANOUT           18
#define PACKET_FANOUT_HASH              0
#define PACKET_FANOUT_LB                1
#endif

static int setup_socket(void)
{
       int err, fd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_IP));
       struct sockaddr_ll ll;
       struct ifreq ifr;
       int fanout_arg;

       if (fd < 0) {
               perror("socket");
               return EXIT_FAILURE;
       }

       memset(&ifr, 0, sizeof(ifr));
       strcpy(ifr.ifr_name, device_name);
       err = ioctl(fd, SIOCGIFINDEX, &ifr);
       if (err < 0) {
               perror("SIOCGIFINDEX");
               return EXIT_FAILURE;
       }

       memset(&ll, 0, sizeof(ll));
       ll.sll_family = AF_PACKET;
       ll.sll_ifindex = ifr.ifr_ifindex;
       err = bind(fd, (struct sockaddr *) &ll, sizeof(ll));
       if (err < 0) {
               perror("bind");
               return EXIT_FAILURE;
       }

       fanout_arg = (fanout_id | (fanout_type << 16));
       err = setsockopt(fd, SOL_PACKET, PACKET_FANOUT,
                        &fanout_arg, sizeof(fanout_arg));
       if (err) {
               perror("setsockopt");
               return EXIT_FAILURE;
       }

       return fd;
}

static void fanout_thread(void)
{
       int fd = setup_socket();
       int limit = 10000;

       if (fd < 0)
               exit(fd);

       while (limit-- > 0) {
               char buf[1600];
               int err;

               err = read(fd, buf, sizeof(buf));
               if (err < 0) {
                       perror("read");
                       exit(EXIT_FAILURE);
               }
               if ((limit % 10) == 0)
                       fprintf(stdout, "(%d) \n", getpid());
       }

       fprintf(stdout, "%d: Received 10000 packets\n", getpid());

       close(fd);
       exit(0);
}

int main(int argc, char **argp)
{
       int fd, err;
       int i;

       if (argc != 3) {
               fprintf(stderr, "Usage: %s INTERFACE {hash|lb}\n", argp[0]);
               return EXIT_FAILURE;
       }

       if (!strcmp(argp[2], "hash"))
               fanout_type = PACKET_FANOUT_HASH;
       else if (!strcmp(argp[2], "lb"))
               fanout_type = PACKET_FANOUT_LB;
       else {
               fprintf(stderr, "Unknown fanout type [%s]\n", argp[2]);
               exit(EXIT_FAILURE);
       }

       device_name = argp[1];
       fanout_id = getpid() & 0xffff;

       for (i = 0; i < 4; i++) {
               pid_t pid = fork();

               switch (pid) {
               case 0:
                       fanout_thread();

               case -1:
                       perror("fork");
                       exit(EXIT_FAILURE);
               }
       }

       for (i = 0; i < 4; i++) {
               int status;

               wait(&status);
       }

       return 0;
}
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