HW12/socket_wrapper.c

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#include <signal.h>
#include <assert.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
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#include <poll.h>
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#include <netdb.h>
#include <string.h>
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#include "socket_wrapper.h"
int getBufferSizeFrom(int sock){
int buffer_sz;
socklen_t len = sizeof(buffer_sz);
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//getsockopt is thread-safe
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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)
{
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ssize_t ret = 0;
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int poll_ret;
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int try = 0;
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struct pollfd fd_single;
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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;
}
}
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assert(0 && "unreachable");
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}
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;
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}
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
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for (i = 0; i < 5; i++)
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{
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ret = getaddrinfo(hostname_str,NULL,&hints,&result);
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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;
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}