udp app to demo OSv issue https://github.com/cloudius-systems/osv/issues/775

Makefile

OSV_SRC=../..
CPPLAGS += -std=c++11
## CPPLAGS += -I$(OSV_SRC) -I$(OSV_SRC)/include/ -I$(OSV_SRC)/arch/x64
CPP=c++ $(CPPLAGS) -ggdb 
CPPSO=$(CPP) -fPIC -shared 
GCC=gcc
GCCSO=$(GCC) -fPIC -shared 


all: udp-rec udp-rec.so
clean:
	rm -f udp-rec udp-rec.so

udp-rec: udp-rec.c 
	$(GCC) -o $@ $<

udp-rec.so: udp-rec.c 
	$(GCCSO) -o $@ $<


module: all

#

udp-rec.c

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define BUFSIZE 1024

/*
 * error - wrapper for perror
 */
void error(char *msg) {
  perror(msg);
  exit(1);
}

int main(int argc, char **argv) {
  int sockfd; /* socket */
  int portno; /* port to listen on */
  int clientlen; /* byte size of client's address */
  struct sockaddr_in serveraddr; /* server's addr */
  struct sockaddr_in clientaddr; /* client addr */
  struct hostent *hostp; /* client host info */
  char buf[BUFSIZE]; /* message buf */
  char *hostaddrp; /* dotted decimal host addr string */
  int optval; /* flag value for setsockopt */
  int n; /* message byte size */

  /* 
   * check command line arguments 
   */
  if (argc != 2) {
    fprintf(stderr, "usage: %s <port>\n", argv[0]);
    exit(1);
  }
  portno = atoi(argv[1]);

  /* 
   * socket: create the parent socket 
   */
  sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  if (sockfd < 0) 
    error("ERROR opening socket");

  /* setsockopt: Handy debugging trick that lets 
   * us rerun the server immediately after we kill it; 
   * otherwise we have to wait about 20 secs. 
   * Eliminates "ERROR on binding: Address already in use" error. 
   */
  optval = 1;
  setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, 
	     (const void *)&optval , sizeof(int));

  /*
   * build the server's Internet address
   */
  bzero((char *) &serveraddr, sizeof(serveraddr));
  serveraddr.sin_family = AF_INET;
  serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
  serveraddr.sin_port = htons((unsigned short)portno);

  /* 
   * bind: associate the parent socket with a port 
   */
  if (bind(sockfd, (struct sockaddr *) &serveraddr, 
	   sizeof(serveraddr)) < 0) 
    error("ERROR on binding");

  /* 
   * main loop: wait for a datagram, then echo it
   */
  clientlen = sizeof(clientaddr);
  while (1) {

    /*
     * recvfrom: receive a UDP datagram from a client
     */
    bzero(buf, BUFSIZE);
#if 0
    n = recvfrom(sockfd, buf, BUFSIZE, 0,
		 (struct sockaddr *) &clientaddr, &clientlen);
    if (n < 0)
      error("ERROR in recvfrom");
   printf("server recvfrom received %d/%d bytes: %s\n", strlen(buf), n, buf);
#else
    struct msghdr msg;
    struct iovec iov;
    iov.iov_base = buf;
    iov.iov_len = BUFSIZE;
    bzero(&msg, sizeof(msg));
    msg.msg_iov = &iov;
    msg.msg_iovlen = 1;
    printf("  AA iov.iov_base = %p\n", iov.iov_base);
    n = recvmsg(sockfd, &msg, 0);
    printf("  BB iov.iov_base = %p\n", iov.iov_base);
    if (n < 0)
      error("ERROR in recvmsg");
    printf("server recvmsg received %d/%d bytes: %s\n", strlen(buf), n, (char*)iov.iov_base);
#endif
    
  }
}

usr.manifest

/udp-app/**: ${MODULE_DIR}/**