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Added files and code for a communication thread that inserts keep-ali…
…ve tokens. This prevents socat from dropping the connection if the communication is idle.
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,161 @@ | ||
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| #define _GNU_SOURCE /* for pipe2 */ | ||
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| #include <sys/types.h> | ||
| #include <fcntl.h> | ||
| #include <stdio.h> | ||
| #include <stdlib.h> | ||
| #include <unistd.h> | ||
| #include <poll.h> | ||
| #include <pthread.h> | ||
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| #include "comm.h" | ||
| #include "mendel.h" | ||
| #include "bebopr.h" | ||
| #include "debug.h" | ||
| #include "beaglebone.h" | ||
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| /* | ||
| * Simple keep alive implementation needed until I find out | ||
| * how to keep the socat connection alive otherwise | ||
| */ | ||
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| static struct pollfd fds[ 4]; | ||
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| static int fd_stdin; | ||
| static int fd_stdout; | ||
| static int alt_stdin; | ||
| static int alt_stdout; | ||
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| static void* comm_thread( void* arg) | ||
| { | ||
| const int timeout = 10000; /* ms */ | ||
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| if (debug_flags & DEBUG_LIMSW) { | ||
| printf( "Socket connection keep-alive thread: started."); | ||
| } | ||
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| // read from system stdin | ||
| fds[ 0].fd = fd_stdin; | ||
| fds[ 0].events = POLLIN | POLLPRI; | ||
| // write to system stdout | ||
| fds[ 1].fd = fd_stdout; | ||
| fds[ 1].events = POLLERR | POLLHUP; | ||
| // read from stdout pipe | ||
| fds[ 2].fd = alt_stdout; | ||
| fds[ 2].events = POLLIN | POLLPRI; | ||
| // write to stdin pipe | ||
| fds[ 3].fd = alt_stdin; | ||
| fds[ 3].events = POLLERR | POLLHUP; | ||
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| while (1) { | ||
| int rc = poll( fds, NR_ITEMS( fds), timeout); | ||
| if (rc < 0) { | ||
| perror( "comm_thread: poll() failed, bailing out!"); | ||
| break; | ||
| } else if (rc == 0) { | ||
| // timeout, send dummy character to keep connection alive | ||
| printf( "%c", 255); | ||
| fflush( stdout); | ||
| fprintf( stderr, "<KEEP ALIVE SENT>\n"); | ||
| } else { | ||
| // input pending | ||
| for (int i = 0 ; i < NR_ITEMS( fds) ; ++i) { | ||
| int events = fds[ i].revents; | ||
| if (events & POLLHUP) { | ||
| if (i == 0) { | ||
| fprintf( stderr, "comm_thread: lost connection on STDIN, closing down.\n"); | ||
| close( alt_stdout); | ||
| close( alt_stdin); | ||
| pthread_exit( NULL); | ||
| } else { | ||
| fprintf( stderr, "Poll on fd %d returns POLLHUP\n", i); | ||
| } | ||
| } else if (events & POLLERR) { | ||
| fprintf( stderr, "Poll on fd %d returns POLLERR\n", i); | ||
| } else if (events & POLLNVAL) { | ||
| fprintf( stderr, "Poll on fd %d returns POLLNVAL\n", i); | ||
| } else if (events & POLLPRI) { | ||
| fprintf( stderr, "Poll on fd %d returns POLLPRI\n", i); | ||
| } else if (events & POLLIN) { | ||
| if (i == 2) { | ||
| // stdout pipe has output for stdout | ||
| char s[ 1]; | ||
| read( fds[ 2].fd, s, sizeof( s)); | ||
| write( fds[ 1].fd, s, sizeof( s)); | ||
| } else if (i == 0) { | ||
| // stdin has input for stdin pipe | ||
| char s[ 1]; | ||
| read( fds[ 0].fd, s, sizeof( s)); | ||
| write( fds[ 3].fd, s, sizeof( s)); | ||
| } else { | ||
| fprintf( stderr, "Poll on fd %d returns POLLIN\n", i); | ||
| } | ||
| } else if (events & POLLOUT) { | ||
| fprintf( stderr, "Poll on fd %d returns POLLOUT\n", i); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| pthread_exit( NULL); | ||
| } | ||
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| static pthread_t worker; | ||
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| /* | ||
| * Fixup file descriptors so that all stdin and stdout of the application | ||
| * is piped to alt_stdout (for stdout) and alt_stdin (for stdin). | ||
| * Now we can watch and modify the datastream from and to the application. | ||
| * That allows us to insert keep-alive characters to keep socat happy! | ||
| */ | ||
| int comm_init( void) | ||
| { | ||
| int result; | ||
| int fds[ 2]; | ||
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| // keep a copy of the program's original fds for stdin and stdout | ||
| fd_stdin = fcntl( 0, F_DUPFD); | ||
| fd_stdout = fcntl( 1, F_DUPFD); | ||
| fprintf( stderr, "fd_stdin = %d, fd_stdout = %d\n", fd_stdin, fd_stdout); | ||
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| // create the stdout pipe with all new fds | ||
| result = pipe2( fds, 0); | ||
| if (result < 0) { | ||
| perror( "stdout pipe creation failed"); | ||
| return -1; | ||
| } | ||
| fprintf( stderr, "stdout pipe created: output side fd = %d, input side fd = %d\n", fds[ 0], fds[ 1]); | ||
| // close application's stdout descriptor (1) | ||
| close( 1); | ||
| // connect input/write side of stdout pipe to application's stdout descriptor (1) | ||
| result = fcntl( fds[ 1], F_DUPFD); | ||
| close( fds[ 1]); | ||
| fds[ 1] = result; | ||
| fprintf( stderr, "stdout pipe fixed: output side fd = %d, input side fd = %d\n", fds[ 0], fds[ 1]); | ||
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| alt_stdout = fds[ 0]; | ||
| fprintf( stderr, "alt_stdout = %d\n", alt_stdout); | ||
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| close( 0); | ||
| result = pipe2( fds, 0); | ||
| if (result < 0) { | ||
| perror( "pipe_out creation failed"); | ||
| return -1; | ||
| } | ||
| fprintf( stderr, "stdin pipe created: output side fd = %d, input side fd = %d\n", fds[ 0], fds[ 1]); | ||
| alt_stdin = fds[ 1]; | ||
| fprintf( stderr, "alt_stdin = %d\n", alt_stdout); | ||
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| result = mendel_thread_create( "comm", &worker, NULL, &comm_thread, NULL); | ||
| if (result != 0) { | ||
| exit( EXIT_FAILURE); | ||
| } | ||
| struct sched_param param = { | ||
| .sched_priority = 74 | ||
| }; | ||
| // SCHED_RR seems to work for now, otherwise use SCHED_FIFO | ||
| pthread_setschedparam( worker, SCHED_RR, ¶m); | ||
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| return 0; | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,8 @@ | ||
| #ifndef _COMM_H | ||
| #define _COMM_H | ||
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| extern int comm_init( void); | ||
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| #endif |
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