HW12/socket_wrapper.c

#include <signal.h>
#include <assert.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <poll.h>
#include <netdb.h>
#include <string.h>
#include "socket_wrapper.h"

int getBufferSizeFrom(int sock){
    int buffer_sz;
    socklen_t len = sizeof(buffer_sz);
    //getsockopt is thread-safe
    if(getsockopt(sock,SOL_SOCKET,SO_SNDBUF,&buffer_sz,&len) < 0){
        perror("failed to get sock buffer size: getsockopt");
        buffer_sz = DEFAULT_BUF_SIZE;/*set to default*/
    }
    if(buffer_sz < MINIMUM_BUF_SIZE)
        buffer_sz = MINIMUM_BUF_SIZE;
    return buffer_sz;
}

ssize_t timeout_recv(int fd,void * buf,size_t n,int timeout)
{
    ssize_t ret = 0;
    int poll_ret;
    int try = 0;
    struct pollfd fd_single;
    timeout = timeout * 1000;
    if (n == 0) return 0;
    for(;;){
        fd_single.fd = fd;
        fd_single.events = POLL_IN;
        poll_ret = (poll(&fd_single,1,timeout));
        if (poll_ret < 0){  fprintf(stderr,"timeout %d\n",timeout); return -1;}
        else if(poll_ret == 0) return -2;
        if (fd_single.revents & POLLHUP) //We'll treat hangups state like timeouts state.
            return -2;
        if ((fd_single.revents & POLLERR) || (fd_single.revents & POLLNVAL))
            return -1;
        if (fd_single.revents & POLL_IN){
            ret = recv(fd,buf,n,0);
            if(ret != 0) return ret;
            //try 3 times
            if (try < 3){
                try++;
                timeout /= 2;
                continue;
            }
            return -2;
        }
    }
    assert(0 && "unreachable");
}

ssize_t recv_until_byte(int fd,void * buf, size_t n,int timeout){
    ssize_t cur = 0;
    uint8_t * b = buf;
    while (cur < n)
    {
        ssize_t r = timeout_recv(fd,&b[cur],n-cur,timeout);
        if (r < 0){
            return r;
        }
        cur += r;
    }
    assert(cur == n);
    return cur;
}

int getsockaddrbyname(int domain,int type, int protocol, const char * hostname_str, struct sockaddr * retaddr){
    struct addrinfo hints;
    struct addrinfo * result, *entry;
    int ret, i;
    memset(&hints,0,sizeof(hints));
    hints.ai_family = domain;
    hints.ai_socktype = type;
    hints.ai_flags = 0;
    hints.ai_protocol = protocol;

    //try 5 times
    for (i = 0; i < 5; i++)
    {
        ret = getaddrinfo(hostname_str,NULL,&hints,&result);
        if(ret == EAI_AGAIN) continue;
        else if (ret != 0) return ret;
        break;
    }
    if (ret != 0) return ret; //maybe name server doesn't work properly.
    
    for (entry = result; entry != NULL; entry = entry->ai_next){
        memcpy(retaddr,entry->ai_addr,sizeof(*retaddr));   
    }
    freeaddrinfo(result);
    return ret;
}