NetBSD Problem Report #48725

From www@NetBSD.org  Mon Apr  7 15:12:35 2014
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Date: Mon,  7 Apr 2014 15:12:34 +0000 (UTC)
From: seanb@netbsd.org
Reply-To: seanb@netbsd.org
To: gnats-bugs@NetBSD.org
Subject: recvmmsg erroneous EAGAIN on nonblocking socket when all msgs aren't filled
X-Send-Pr-Version: www-1.0

>Number:         48725
>Category:       kern
>Synopsis:       recvmmsg erroneous EAGAIN on nonblocking socket when all msgs aren't filled
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    seanb
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Apr 07 15:15:00 +0000 2014
>Closed-Date:    Mon Apr 07 15:41:12 +0000 2014
>Last-Modified:  Mon Apr 07 15:41:12 +0000 2014
>Originator:     Sean Boudreau
>Release:        6.99.39
>Organization:
NetBSD
>Environment:
NetBSD  6.99.39 NetBSD 6.99.39 (seanb) #4: Wed Apr  2 11:39:05 EDT 2014  seanb@:/home/seanb/cvs_netbsd/HEAD/src/sys/arch/i386/compile/obj/seanb i386
>Description:
An erroneous EAGAIN can be returned when receiving on a non-blocking socket with recvmmsg with a mmsg array containing multiple members.  This occurs when some, but not all of the mmsg array members are filled with data.
>How-To-Repeat:
#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <pthread.h>
#include <string.h>
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <time.h>
#include <poll.h>
#include <err.h>

#define MAX_PACKETS 2
#define BUFSIZE 2048

void *
runRecvThread(void *arg)
{
	struct pollfd pfd;
	int ret, fd;
	struct mmsghdr	msgs[MAX_PACKETS];
	struct iovec	iovecs[MAX_PACKETS];
	char		bufs[MAX_PACKETS][BUFSIZE+1];
	int		retval, i;

	fd = *(int *)arg;
	pfd.fd = fd;
	pfd.events = POLLIN;
	pfd.revents = 0;

	memset(msgs, 0, sizeof(msgs));

	for (i = 0; i < MAX_PACKETS; i++){
		iovecs[i].iov_base = bufs[i];
		iovecs[i].iov_len = BUFSIZE;
		msgs[i].msg_hdr.msg_name = NULL;
		msgs[i].msg_hdr.msg_namelen = 0;
		msgs[i].msg_hdr.msg_control = NULL;
		msgs[i].msg_hdr.msg_controllen = 0;
		msgs[i].msg_hdr.msg_flags = 0;
		msgs[i].msg_hdr.msg_iovlen = 1;
		msgs[i].msg_hdr.msg_iov = &iovecs[i];
		msgs[i].msg_hdr.msg_iovlen = 1;
	}

	for (;;) {
		ret = poll(&pfd, 1, -1);
		if (ret == 1 && (pfd.revents & POLLIN)) {
			retval = recvmmsg(fd, msgs, MAX_PACKETS, 0, 0);
			if (retval == -1)
				err(1, "recvmmsg");
			printf("got data %d\n", retval);
			for (i = 0; i < retval; i++)
				printf("\t%d %s\n", i, bufs[i]);
		} else {
			errx(1, "unexpected return from poll: %d\n", ret);
		}
	}
}

int
main(int argc, char *argv[])
{
	int fds[2];
	pthread_t recvT;

	if (socketpair(AF_LOCAL, SOCK_DGRAM, 0, fds) == -1)
		err(1, "socketpair");

	fcntl(fds[1], F_SETFL, fcntl(fds[1], F_GETFL, 0) | O_NONBLOCK);
	pthread_create(&recvT, NULL, &runRecvThread, &fds[1]);
	for (;;) {
		sleep(1);
		send(fds[0], "data\n", sizeof("data\n"), 0);
	}
	pthread_join(recvT, NULL);
	return 0;
}
>Fix:

>Release-Note:

>Audit-Trail:

Responsible-Changed-From-To: kern-bug-people->seanb
Responsible-Changed-By: seanb@NetBSD.org
Responsible-Changed-When: Mon, 07 Apr 2014 15:15:54 +0000
Responsible-Changed-Why:
Taking


From: "Sean Boudreau" <seanb@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/48725 CVS commit: src/sys/kern
Date: Mon, 7 Apr 2014 15:35:23 +0000

 Module Name:	src
 Committed By:	seanb
 Date:		Mon Apr  7 15:35:23 UTC 2014

 Modified Files:
 	src/sys/kern: uipc_syscalls.c

 Log Message:
 Fix a case where an erroneous EAGAIN was returned out of recvmmsg.
 This occured when some, but not all of the mmsg array members
 were filled with data from a non-blocking socket.
 PR kern/48725


 To generate a diff of this commit:
 cvs rdiff -u -r1.165 -r1.166 src/sys/kern/uipc_syscalls.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->closed
State-Changed-By: seanb@NetBSD.org
State-Changed-When: Mon, 07 Apr 2014 15:41:12 +0000
State-Changed-Why:
Fixed.


>Unformatted:

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