A simple MPI code to catch the SIGUSR1, SIGTERM signals with signalfd unix system call
#include <assert.h>
#include <poll.h>
#include <signal.h>
#include <stdio.h>
#include <sys/signalfd.h>
#include <unistd.h>
#include <mpi.h>
/*Simple MPI Code*/
int main(int argc, char* argv[]){
MPI_Init(&argc, &argv);
int err, nbProcs, rank;
sigset_t sigset;
int fd;
MPI_Comm_size(MPI_COMM_WORLD, &nbProcs);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
****
Setup SIGALRM to be delivered via SignalFD
****
sigset_t mask;
sigemptyset(&mask);
sigaddset(&mask, SIGTERM);
sigaddset(&mask, SIGUSR1);
/* */
if (sigprocmask(SIG_BLOCK, &mask, NULL) < 0) {
printf("Failed to signalmask\n");
return -1;
}
fd = signalfd(-1, &mask, 0);
if (fd < 0)
return -1;
while (1) {
struct signalfd_siginfo si;
int ret;
ret = read(fd, &si, sizeof(si));// here the MPI process doesn't
return when I send SIGTERM or SIGUSR1
if (ret < 0)
return -1;
if (ret != sizeof(si))
return -1;
if (si.ssi_signo == SIGTERM)
printf("receive SIGTERM \\\n");
else if (si.ssi_signo == SIGUSR1)
printf("receive SIGUSR1\n");
}
MPI_Finalize();
return 0;
}
In this code, I am using signalfd to catch SIGUSR1, SIGTERM. At
ret = read(fd, &si, sizeof(si));
read() system call it doesn't return and the program dies at this point. When I use the same code without MPI simple C code it works perfect.Can anyone explain me how does signalfd works inside MPI???
Related
I am trying to use serial communication in Raspberry Pi. I found this link. I made only one change in the code and increase the buffer value to 30. Here my edited code:-
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
int main(int argc, char* argv[]) {
struct termios serial;
char* str = "Hello";
char buffer[30];
if (argc == 1) {
printf("Usage: %s [device]\n\n", argv[0]);
return -1;
}
printf("Opening %s\n", argv[1]);
int fd = open(argv[1], O_RDWR | O_NOCTTY | O_NDELAY);
if (fd == -1) {
perror(argv[1]);
return -1;
}
if (tcgetattr(fd, &serial) < 0) {
perror("Getting configuration");
return -1;
}
// Set up Serial Configuration
serial.c_iflag = 0;
serial.c_iflag = 0;
serial.c_oflag = 0;
serial.c_lflag = 0;
serial.c_cflag = 0;
serial.c_cc[VMIN] = 0;
serial.c_cc[VTIME] = 0;
serial.c_cflag = B115200 | CS8 | CREAD;
tcsetattr(fd, TCSANOW, &serial); // Apply configuration
// Attempt to send and receive
printf("Sending: %s\n", str);
//int wcount = write(fd, &str, strlen(str));
int wcount = write(fd, str, strlen(str));
if (wcount < 0) {
perror("Write");
return -1;
}
else {
printf("Sent %d characters\n", wcount);
}
// int rcount = read(fd, &buffer, sizeof(buffer));
int rcount = read(fd, buffer, sizeof(buffer));
if (rcount < 0) {
perror("Read");
return -1;
}
else {
printf("Received %d characters\n", rcount);
}
buffer[rcount] = '\0';
printf("Received: %s\n", buffer);
close(fd);
}
I short Rx and Tx pin and run this code. I should receive "Hello" but I am getting this:-
Received: pi#raspberrypi:~$ Hello
So, it is clear that I am receiving "Hello" but additionally I am automatically transmitting
pi#raspberrypi:~$
So, please tell me I to stop transmitting my user name.
I'm writing a code for extraction of peer credential by the server process connected through ipc using domain sockets to the client process. There is no error in the code but while running it I don't get the euid and gid of the peer process.
Code for server process is:
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
//#include<ucred.h>
#define SCM_CREDENTIALS
# define UNIX_PATH_MAX 100
int getpeereid(int connection_fd,uid_t euid,gid_t gid)
{
struct ucred cred;
socklen_t len = sizeof(cred);
if (getsockopt(connection_fd, SOL_SOCKET, SO_PEERCRED, &cred, &len) < 0)
return (-1);
euid =cred.uid;
gid = cred.gid;
//int passcred=1;
//setsockopt(connection_fd,SOL_SOCKET,SO_PASSCRED,(void *)&passcred,sizeof(passcred));
printf("effective user id", euid);
printf("effective group id",gid);
return 0;
}
int connection_handler(int connection_fd)
{
int nbytes;
char buffer[1024];
char msg[256];
//while(cont=recv(connection_fd,buffer,sizeof(buffer),0)>0)
//{
//write(1,buffer,cont)
nbytes = read(connection_fd, buffer, 256);
buffer[nbytes] = 0;
printf("MESSAGE FROM CLIENT: %s\n", buffer);
printf("enter the message");
scanf("%s",msg);
nbytes = snprintf(buffer, 256,msg);
write(connection_fd, buffer, nbytes);
//}
close(connection_fd);
return 0;
}
int main(void)
{
struct sockaddr_un address;
int socket_fd, connection_fd,res;
socklen_t address_length;
pid_t child;
uid_t eid;
gid_t gid;
socket_fd = socket(PF_UNIX, SOCK_STREAM, 0);
if(socket_fd < 0)
{
printf("socket() failed\n");
return 1;
}
printf("socket created\n");
unlink("./demo_socket");
/* start with a clean address structure */
memset(&address, 0, sizeof(struct sockaddr_un));
address.sun_family = AF_UNIX;
snprintf(address.sun_path, UNIX_PATH_MAX, "./demo_socket");
if(bind(socket_fd,
(struct sockaddr *) &address,
sizeof(struct sockaddr_un)) != 0)
{
printf("bind() failed\n");
return 1;
}
if(listen(socket_fd, 5) != 0)
{
printf("listen() failed\n");
return 1;
}
while((connection_fd = accept(socket_fd,
(struct sockaddr *) &address,
&address_length)) > -1)
{
// get the credentials
res=getpeereid(connection_fd,geteuid(),getgid());
if (res==0)
{
//if(res==0)
//{
child = fork();
if(child == 0)
{
/* now inside newly created connection handling process */
return connection_handler(connection_fd);
}
}
/* still inside server process */
close(connection_fd);
//}
}
close(socket_fd);
unlink("./demo_socket");
return 0;
}
the code for client
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <string.h>
#define UNIX_PATH_MAX 100
int connection_handler(int socket_fd)
{
int nbytes;
char buffer[1024];
char mesg[256];
printf("enter the message");
scanf("%s",mesg);
//printf("message is %s",mesg);
nbytes = snprintf(buffer, 256,mesg);
//fgets(buffer,256,mesg);
//i=atoi(mesg);
write(socket_fd,buffer,nbytes);
//send(socket_fd,mesg,sizeof(mesg),0);
}
//nbytes = read(socket_fd, buffer, 256);
//buffer[nbytes] = 0;
//printf("MESSAGE FROM SERVER: %s\n", buffer);
//}
int main(void)
{
struct sockaddr_un address;
int socket_fd, nbytes,i;
pid_t child;
char buffer[256];
//char mesg[100];
socket_fd = socket(PF_UNIX, SOCK_STREAM, 0);
if(socket_fd < 0)
{
printf("socket() failed\n");
return 1;
}
printf("socket created\n");
/* start with a clean address structure */
memset(&address, 0, sizeof(struct sockaddr_un));
address.sun_family = AF_UNIX;
snprintf(address.sun_path, UNIX_PATH_MAX, "./demo_socket");
if(connect(socket_fd,
(struct sockaddr *) &address,
sizeof(struct sockaddr_un)) != 0)
{
printf("connect() failed\n");
return 1;
}
child=fork();
while(child==0)
{
return connection_handler(socket_fd);
//printf("connection established\n");
//printf("enter the message");
//scanf("%s",mesg);
//printf("message is %s",mesg);
//bytes = snprintf(buffer, 256,mesg);
//fgets(buffer,256,mesg);
//i=atoi(mesg);
//write(socket_fd,buffer,nbytes);
//send(socket_fd,mesg,sizeof(mesg),0);
}
nbytes = read(socket_fd, buffer, 256);
buffer[nbytes] = 0;
printf("MESSAGE FROM SERVER: %s\n", buffer);
close(socket_fd);
return 0;
}
See http://www.thomasstover.com/uds.html for good overview.
If the server is Linux, the main problem is missing _GNU_SOURCE. Full patch below, it has a few minor changes just to get rid of gcc -Wall -Werror -pedantic -std=c99 errors and warnings.
--- server.c.orig 2014-12-06 13:23:09.138472871 +0200
+++ server.c 2014-12-06 13:21:31.962475754 +0200
## -1,3 +1,4 ##
+#define _GNU_SOURCE
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
## -5,7 +6,6 ##
#include <unistd.h>
#include <string.h>
//#include<ucred.h>
-#define SCM_CREDENTIALS
# define UNIX_PATH_MAX 100
int getpeereid(int connection_fd,uid_t euid,gid_t gid)
## -20,8 +20,8 ##
//int passcred=1;
//setsockopt(connection_fd,SOL_SOCKET,SO_PASSCRED,(void *)&passcred,sizeof(passcred));
-printf("effective user id", euid);
-printf("effective group id",gid);
+printf("effective user id %d", euid);
+printf("effective group id %d",gid);
return 0;
}
## -40,7 +40,7 ##
printf("MESSAGE FROM CLIENT: %s\n", buffer);
printf("enter the message");
scanf("%s",msg);
-nbytes = snprintf(buffer, 256,msg);
+nbytes = snprintf(buffer, 256, "%s", msg);
write(connection_fd, buffer, nbytes);
//}
close(connection_fd);
## -54,8 +54,6 ##
int socket_fd, connection_fd,res;
socklen_t address_length;
pid_t child;
-uid_t eid;
-gid_t gid;
socket_fd = socket(PF_UNIX, SOCK_STREAM, 0);
if(socket_fd < 0)
I've written a code using SOL_SOCKET protocol but getting error as 10043 (error in socket).
The code is as follows:
#include <QCoreApplication>
#include<QDebug>
//#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
/****************************************/
#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")
/****************************************/
#define DEFAULT_BUFLEN 512
int recvbuflen = DEFAULT_BUFLEN;
char recvbuf[DEFAULT_BUFLEN];
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
WSADATA wsaData;
int iResult;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
}
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
ZeroMemory( &hints, sizeof(hints) );
//hints.ai_family = AF_UNSPEC;
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = SOL_SOCKET;
//hints.ai_protocol = IPPROTO_TCP;
#define DEFAULT_PORT "10990"
// Resolve the server address and port
iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);
if (iResult != 0) {
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
SOCKET ConnectSocket = INVALID_SOCKET;
// Attempt to connect to the first address returned by
// the call to getaddrinfo
ptr=result;
// Create a SOCKET for connecting to server
ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype,
ptr->ai_protocol);
if (ConnectSocket == INVALID_SOCKET) {
printf("Error at socket(): %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
int rcvbuf = 8192; /* recv buffer size */
int z = setsockopt(ConnectSocket,SOL_SOCKET,SO_RCVBUF,
(char*)&rcvbuf,sizeof(rcvbuf));
do {
iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
if (iResult > 0)
printf("Bytes received: %d\n", iResult);
else if (iResult == 0)
printf("Connection closed\n");
else
printf("recv failed: %d\n", WSAGetLastError());
} while (iResult > 0);
return a.exec();
}
When I run it shows::
Error in socket:10043
I googled it and found that the error is because of wrong protocol for the socket type,I tried to find the correct protocol and socket type match but couldn't find.I tried every possible socket option and protocol match.
Any body facing the same problem?
You're putting the wrong value in the ai_protocol field. It needs to be one of the IPPROTO_ constants (like e.g. IPPROTO_TCP or IPPROTO_ICMP).
SOL_SOCKET is used to set socket options (like you do later in the code).
You should normally not set that member, except to zero.
I have a simple program written in C which uses termios to send a basic string to the Raspberry Pi UART and attempts to read and output the response. The Rx and Tx pins on the Raspberry Pi are connected with a jumper so whatever is sent should be immediately received.
Despite the program outputting that it successfully sent and received 5 characters for the chosen string ('Hello'), trying to print the contents of the buffer just produces one or two garbage characters.
The program:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
int main(int argc, char* argv[]) {
struct termios serial;
char* str = "Hello";
char buffer[10];
if (argc == 1) {
printf("Usage: %s [device]\n\n", argv[0]);
return -1;
}
printf("Opening %s\n", argv[1]);
int fd = open(argv[1], O_RDWR | O_NOCTTY | O_NDELAY);
if (fd == -1) {
perror(argv[1]);
return -1;
}
if (tcgetattr(fd, &serial) < 0) {
perror("Getting configuration");
return -1;
}
// Set up Serial Configuration
serial.c_iflag = 0;
serial.c_oflag = 0;
serial.c_lflag = 0;
serial.c_cflag = 0;
serial.c_cc[VMIN] = 0;
serial.c_cc[VTIME] = 0;
serial.c_cflag = B115200 | CS8 | CREAD;
tcsetattr(fd, TCSANOW, &serial); // Apply configuration
// Attempt to send and receive
printf("Sending: %s\n", str);
int wcount = write(fd, &str, strlen(str));
if (wcount < 0) {
perror("Write");
return -1;
}
else {
printf("Sent %d characters\n", wcount);
}
int rcount = read(fd, &buffer, sizeof(buffer));
if (rcount < 0) {
perror("Read");
return -1;
}
else {
printf("Received %d characters\n", rcount);
}
buffer[rcount] = '\0';
printf("Received: %s\n", buffer);
close(fd);
}
Outputs:
Opening /dev/ttyAMA0
Sending: Hello
Sent 5 characters
Received 5 characters
Received: [garbage]
I can't see any major problem with the code myself, but I might be wrong. I can successfully send and receive characters using PuTTY connected with the same settings, so it can't really be a hardware problem. Although I haven't tried it in PuTTY, trying to connect with anything less than 115200 baud with this program will result in nothing being received.
Where am I going wrong?
int wcount = write(fd, &str, strlen(str));
int rcount = read(fd, &buffer, sizeof(buffer));
In these lines, buffer/str are already pointers. You are passing a pointer to a pointer.
The lines should be:
int wcount = write(fd, str, strlen(str));
int rcount = read(fd, buffer, sizeof(buffer));
what happens when a UDP packet is sent to a host using sendto().
all the bits i am sending are sent(known from the return value).immediately i use a recvfrom() which does not output anything but program do not exit(i.e no return value).
I think that the program must exit if no reply is recieved.
what will the replies for a UDP packet from a port.
is this packet blocked by firewall?? if yes then why is the return value of sendto is non-negative.
recvfrom() will block until a message is received unless you set the socket to non-blocking.
The interfaces you want to look for are
ioctl() with FIONBIO or O_NONBLOCK (depending your platform),
select() to wait for data to arrive, or timeout after a while
Also remember that the address and port number for sendto() usually be network-byte order, so look into ntohl and ntohs.
you must have some error in your client or server. try localhost first, so you avoid firewall problems
this is an example of nonblocking udp client/server I was using for my tests, it uses ioctl() to check if there is data to read on the socket, however if you want to do some serious application using epoll would be more efficient also you can specify timeout to wait in microseconds:
[null#localhost tests]$ cat udpserv.c
#include <stdlib.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <errno.h>
#define BUFLEN 512
#define NPACK 15
#define PORT 9930
void diep(char *s)
{
printf("erno=%d errstr=%s\n",errno,strerror(errno));
perror(s);
exit(1);
}
int main(void)
{
struct sockaddr_in si_me, si_other;
int s,ret,nbytes, i, slen=sizeof(si_other);
char buf[BUFLEN];
if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
diep("socket");
memset((char *) &si_me, 0, sizeof(si_me));
si_me.sin_family = AF_INET;
si_me.sin_port = htons(PORT);
si_me.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(s, (struct sockaddr*) &si_me, sizeof(si_me))==-1)
diep("bind");
fcntl(s, F_SETFL, fcntl(s, F_GETFL, 0) | O_NONBLOCK);
sleep(10);
for (i=0; i<NPACK; i++) {
ret=ioctl(s,FIONREAD,&nbytes);
if (ret==-1) {
printf("error on FIONREAD\n");
} else {
printf("nbytes=%d\n",nbytes);
}
if (recvfrom(s, buf, BUFLEN, 0, (struct sockaddr*) &si_other, &slen)==-1)
diep("recvfrom()");
printf("Received first half of packet from %s:%d\nData: %s\n\n",
inet_ntoa(si_other.sin_addr), ntohs(si_other.sin_port), buf);
}
close(s);
return 0;
}
[null#localhost tests]$ cat udpclient.c
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#define SRV_IP "127.0.0.1"
#define BUFLEN 200
#define NPACK 10
#define PORT 9930
/* diep(), #includes and #defines like in the server */
void diep(char *s)
{
perror(s);
exit(1);
}
int main(void)
{
struct sockaddr_in si_other;
int s, i, slen=sizeof(si_other);
char buf[BUFLEN];
if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
diep("socket");
memset((char *) &si_other, 0, sizeof(si_other));
si_other.sin_family = AF_INET;
si_other.sin_port = htons(PORT);
if (inet_aton(SRV_IP, &si_other.sin_addr)==0) {
fprintf(stderr, "inet_aton() failed\n");
exit(1);
}
for (i=0; i<NPACK; i++) {
printf("Sending packet %d\n", i);
sprintf(buf, "This is packet %d\n", i);
if (sendto(s, buf, BUFLEN, 0, (struct sockaddr*) &si_other, slen)==-1)
diep("sendto()");
}
close(s);
return 0;
}
the sendto() is non negative because it returns number of bytes sent. check the man page for sendto