Re: kern/54435: reading TCP urgent data with MSG_OOB doesn't clear poll(2) status

[Valery Ushakov <uwe%stderr.spb.ru@localhost>]

The following reply was made to PR kern/54435; it has been noted by GNATS.

From: Valery Ushakov <uwe%stderr.spb.ru@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/54435: reading TCP urgent data with MSG_OOB doesn't clear
 poll(2) status
Date: Sun, 4 Aug 2019 02:36:37 +0300

 Updated test, so that we are on the same page.
 
 /* oobrecv.c */
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/ioctl.h>
 
 #include <err.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <poll.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
 #include <netinet/in.h>
 #include <arpa/inet.h>
 
 int usage(void);
 int getsocket(void);
 void oobtest(int);
 int pollsock(int);
 
 bool oobinline = false;
 bool oobsync = false;
 bool delay = false;
 
 int
 usage(void)
 {
     fprintf(stderr, "usage: oobrecv [oob | inline | sync | delay | sleep] ...\n");
     fprintf(stderr, "default is: %s%s%s\n",
 	    oobinline ? "inline" : "oob",
 	    oobsync ? " sync" : "",
 	    delay ? " delay" : "");
 
     return EXIT_FAILURE;
 }
 
 
 int
 main(int argc, char **argv)
 {
     int i;
 
     for (i = 1; i < argc; ++i) {
 	if (strcasecmp(argv[i], "oob") == 0)
 	    oobinline = false;
 	else if (strcasecmp(argv[i], "inline") == 0)
 	    oobinline = true;
 	else if (strcasecmp(argv[i], "delay") == 0
 		 || strcasecmp(argv[i], "sleep") == 0)
 	    delay = true;
 	else if (strcasecmp(argv[i], "sync") == 0)
 	    oobsync = true;
 	else
 	    return usage();
     }
 
     oobtest(getsocket());
     return 0;
 }
 
 
 int
 getsocket(void)
 {
     int s;
     int status;
 
     s = socket(PF_INET, SOCK_STREAM, 0);
     if (s < 0)
 	err(EXIT_FAILURE, "socket");
 
     struct sockaddr_in sin;
     memset(&sin, 0, sizeof(sin));
 #if !defined(__linux__) && !defined(__sun__)
     sin.sin_len = sizeof(sin);
 #endif
     sin.sin_family = AF_INET;
     sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
     sin.sin_port = htons(12345);
 
     if (oobinline) {
 	int one = 1;
 	status = setsockopt(s, SOL_SOCKET, SO_OOBINLINE,
 			    (char *)&one, sizeof(one));
 	if (status < 0)
 	    err(EXIT_FAILURE, "SO_OOBINLINE");
     }
 
     status = connect(s, (struct sockaddr *)&sin, sizeof(sin));
     if (status < 0)
 	err(EXIT_FAILURE, "connect");
 
     return s;
 }
 
 
 void
 oobtest(int s)
 {
     char buf[128];
     int status;
 
     printf("reading urgent data with %s",
 	   oobinline ? "SO_OOBINLINE" : "MSG_OOB");
     if (oobsync)
 	printf(" with SIOCATMARK");
     if (delay)
 	printf(" after delay");
     printf("\n");
 
     if (delay)
 	sleep(1);
 
     for (;;) {
 	int revents = pollsock(s);
 	if (revents == 0)
 	    continue;
 
 	if (revents & POLLNVAL) {
 	    errno = EBADF;
 	    err(EXIT_FAILURE, "poll");
 	}
 
 	if (revents & POLLERR) {
 	    int sockerr;
 	    socklen_t optlen = (socklen_t)sizeof(sockerr);
 
             status = getsockopt(s, SOL_SOCKET, SO_ERROR,
 				(char *)&sockerr, &optlen);
 	    if (status < 0)
 		err(EXIT_FAILURE, "SO_ERROR");
 
 	    errno = sockerr;
 	    err(EXIT_FAILURE, NULL);
 	}
 
 	ssize_t nread;
 
 	if (oobsync && (revents & (POLLPRI | POLLRDBAND))) {
 	    for (;;) {
 		int atmark;
 		status = ioctl(s, SIOCATMARK, &atmark);
 		if (status < 0)
 		    err(EXIT_FAILURE, "SIOCATMARK");
 
 		if (atmark) {
 		    printf("<at mark>\n");
 		    break;
 		}
 
 		nread = recv(s, buf, sizeof(buf), 0);
 		if (nread < 0)
 		    err(EXIT_FAILURE, "recv");
 
 		printf("recv() = %zd (reading to mark)\n", nread);
 		fwrite(buf, 1, nread, stdout);
 		printf("\n");
 	    }
 	}
 
 	int flags = 0;
 	if (!oobinline && (revents & (POLLPRI | POLLRDBAND)))
 	    flags |= MSG_OOB;
 
       retry:
 	nread = recv(s, buf, sizeof(buf), flags);
 
 	if (nread < 0) {
 	    if (flags & MSG_OOB) {
 		flags &= ~MSG_OOB;
 		printf("recv(MSG_OOB) failed, retrying\n");
 		goto retry;
 	    }
 	    else {
 		err(EXIT_FAILURE, "recv%s",
 		    flags & MSG_OOB ? "(MSG_OOB)" : "");
 	    }
 	}
 
 	printf("recv(%s) = %zd\n",
 	       flags & MSG_OOB ? "MSG_OOB" : "",
 	       nread);
 
 	if (nread == 0)
 	    return;
 
 	fwrite(buf, 1, nread, stdout);
 	printf("\n");
     }
 }
 
 
 int
 pollsock(int s)
 {
     struct pollfd fds[1];
 
     fds[0].fd = s;
     fds[0].events = POLLIN | POLLPRI | POLLRDBAND;
     fds[0].revents = 0;
 
     int nready = poll(fds, 1, -1);
     if (nready < 0)
 	err(EXIT_FAILURE, "poll");
 
     if (nready == 0)
 	return 0;
 
     int revents = fds[0].revents;
 
     printf("poll: revents = 0x%x", revents);
     if (fds[0].revents != 0) {
 	printf(":");
 	if (revents & POLLNVAL)   printf(" NVAL");
 	if (revents & POLLERR) 	  printf(" ERR");
 	if (revents & POLLHUP) 	  printf(" HUP");
 	if (revents & POLLIN)  	  printf(" IN");
 	if (revents & POLLPRI) 	  printf(" PRI");
 	if (revents & POLLRDNORM) printf(" RDNORM");
 	if (revents & POLLRDBAND) printf(" RDBAND");
     }
     printf("\n");
 
     return revents;
 }