* Problems of AF_INET domain socket regarding out-of-band data.
@ 2018-06-13 15:02 Takashi Yano
2018-06-21 1:35 ` Takashi Yano
0 siblings, 1 reply; 3+ messages in thread
From: Takashi Yano @ 2018-06-13 15:02 UTC (permalink / raw)
To: cygwin
[-- Attachment #1: Type: text/plain, Size: 1594 bytes --]
Hello,
I have found a few problems of AF_INET domain socket regarding
out-of-band data.
1. recv() with MSG_OOB flag eats normal data if no OOB data
is sent yet.
2. Calling recv() with MSG_OOB flag is blocked if no OOB data
is sent yet.
3. Calling recv() without MSG_OOB flag after receiving OOB data
is blocked even if received data exist in buffer.
Regarding problem 1 and 2, POSIX states as follows about recv().
[EINVAL]
The MSG_OOB flag is set and no out-of-band data is available.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/recv.html
Attached is a sample program to reproduce these problems.
Argument to this program specifies the test mode.
0: cause problem 1
2: cause problem 2
3: cause problem 3
Expected results:
debian:~/OOB> ./server_client 0
recv(OOB): Invalid argument
OOB : (-1)
NORMAL: 1234567890 (10)
debian:~/OOB> ./server_client 1
OOB : A (1)
NORMAL: 1234567890 (10)
debian:~/OOB> ./server_client 2
recv(OOB): Invalid argument
OOB : (-1)
NORMAL: 1234567890 (10)
debian:~/OOB> ./server_client 3
OOB : A (1)
NORMAL: 1234567890 (10)
debian:~/OOB>
Result on cygwin:
[yano@Express5800-S70 ~/OOB]$ ./server_client 0
OOB : 1234567890 (10)
NORMAL: (0)
[yano@Express5800-S70 ~/OOB]$ ./server_client 1
OOB : A (1)
NORMAL: 1234567890 (10)
[yano@Express5800-S70 ~/OOB]$ ./server_client 2
[yano@Express5800-S70 ~/OOB]$ ./server_client 3
OOB : A (1)
[yano@Express5800-S70 ~/OOB]$
Only the result of test mode 1 is as expected.
I have confirmed this occurs in both latest 32bit and 64 bit
cygwin.
--
Takashi Yano <takashi.yano@nifty.ne.jp>
[-- Attachment #2: server_client.c --]
[-- Type: text/x-csrc, Size: 2632 bytes --]
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <signal.h>
#include <sys/wait.h>
#define PORT 12345
#define HOST "127.0.0.1"
int server(int mode)
{
int sock0, sock1;
struct sockaddr_in addr;
struct sockaddr_in client;
socklen_t len;
/* Create a socket */
sock0 = socket(AF_INET, SOCK_STREAM, 0);
if (sock0 < 0) {
perror("socket");
return -1;
}
/* Bind */
addr.sin_family = AF_INET;
addr.sin_port = htons(PORT);
addr.sin_addr.s_addr = INADDR_ANY;
if (bind(sock0, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
perror("bind");
return -1;
}
/* Wait for connection from client */
if (listen(sock0, 1) < 0) {
perror("listen");
return -1;
}
/* Accept connection */
len = sizeof(client);
sock1 = accept(sock0, (struct sockaddr *)&client, &len);
if (sock1 < 0) {
perror("accept");
return -1;
}
/* Send normal data */
if (send(sock1, "1234567890", 10, 0) < 0) {
perror("send");
return -1;
}
if (mode & 1) {
/* Send out-of-band data */
if (send(sock1, "A", 1, MSG_OOB) < 0) {
perror("send(OOB)");
return -1;
}
}
/* Wait for receiving all data at client side */
usleep(200000);
if (mode & 2) {
return -1; /* return -1 to kill client */
}
/* Close client socket */
close(sock1);
/* Close socket for listen */
close(sock0);
return 0;
}
int client()
{
struct sockaddr_in server;
int sock;
char buf[256];
int n;
/* Create a socket */
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock < 0) {
perror("sock");
return -1;
}
/* Setting for connection */
server.sin_family = AF_INET;
server.sin_port = htons(PORT);
server.sin_addr.s_addr = inet_addr(HOST);
/* Connect to server */
if (connect(sock, (struct sockaddr *)&server, sizeof(server)) < 0) {
perror("connect");
return -1;
}
/* Wait for sending all data at server side */
usleep(100000);
/* Receive out-of-band data from server */
memset(buf, 0, sizeof(buf));
n = recv(sock, buf, sizeof(buf), MSG_OOB);
if (n<0) {
perror("recv(OOB)");
}
printf("OOB : %s (%d)\n", buf, n);
/* Receive normal data from server */
memset(buf, 0, sizeof(buf));
n = recv(sock, buf, sizeof(buf), 0);
if (n<0) {
perror("recv");
}
printf("NORMAL: %s (%d)\n", buf, n);
/* Close socket */
close(sock);
return 0;
}
int main(int argc, char *argv[])
{
int mode = 0;
pid_t pid;
if (argc >= 2) {
mode = atoi(argv[1]);
}
pid = fork();
if (pid) {
if (server(mode) < 0) kill(pid, SIGTERM);
wait(NULL);
} else {
return client();
}
return 0;
}
[-- Attachment #3: Type: text/plain, Size: 219 bytes --]
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Problems of AF_INET domain socket regarding out-of-band data.
2018-06-13 15:02 Problems of AF_INET domain socket regarding out-of-band data Takashi Yano
@ 2018-06-21 1:35 ` Takashi Yano
2018-06-21 14:05 ` Corinna Vinschen
0 siblings, 1 reply; 3+ messages in thread
From: Takashi Yano @ 2018-06-21 1:35 UTC (permalink / raw)
To: cygwin
[-- Attachment #1: Type: text/plain, Size: 1833 bytes --]
Hi Corinna,
On Wed, 13 Jun 2018 22:48:58 +0900
Takashi Yano wrote:
> 1. recv() with MSG_OOB flag eats normal data if no OOB data
> is sent yet.
>
> 2. Calling recv() with MSG_OOB flag is blocked if no OOB data
> is sent yet.
>
> 3. Calling recv() without MSG_OOB flag after receiving OOB data
> is blocked even if received data exist in buffer.
I looked into these problems and found these are due to bug of
cygwin1.dll.
Problem 1:
If recv() is called with MSG_OOB, in fhandler_socket_inet::
recv_internal(), wsamsg->dwFlags with MSG_OOB flag set is passed
to WSARecv() and this fails because no OOB data exists. At this time,
wsamsg-> dwFlags is modified by WSARecv() so that it does not have
the MSG_OOB flag. Then, WSARecv() is called again without MSG_OOB
flag in while loop. At this time, normal data is read and returned.
Problem 2:
In fhandler_socket_inet::recv_internal(), wait_for_events() is
called. This blocks the call until OOB data arrives.
Problem 3:
If recv() is called with MSG_OOB flag set, fhandler_socket_inet::
recv_internal() calls wait_for_events() with both FD_OOB and
FD_READ. If both OOB data and normal data already arrived,
not only the event of FD_OOB but also the event of FD_READ are
reset to non signaled state. I'm not sure where the signal is
reset, though.
Moreover, return value of ioctl command SIOCATMARK of winsock
is not as expected. In winsock, SIOCATMARK returns TRUE if no
OOB data exists, FALSE otherwise. This is almost opposite to
expectation.
Furthermore, inline mode (SO_OOBINLINE) of winsock is completely
broken. If SO_OOBINLINE is set, SIOATMARK always returns TRUE.
This means application cannot determine OOB data at all in inline
mode.
To solve these problems, I made a patch attached.
Could you please have a look?
--
Takashi Yano <takashi.yano@nifty.ne.jp>
[-- Attachment #2: 0001-Fix-the-handling-of-out-band-data-OOB-in-a-socket.patch --]
[-- Type: application/octet-stream, Size: 13017 bytes --]
From 63497ad1d5089beb21a63c62de3c662faf42881f Mon Sep 17 00:00:00 2001
From: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Wed, 20 Jun 2018 14:47:27 +0900
Subject: [PATCH] Fix the handling of out-band-data (OOB) in a socket.
* fhandler.h (class fhandler_socket_wsock): Add variable bool oobinline.
* fhandler_socket_inet.cc (fhandler_socket_wsock::fhandler_socket_wsock):
Add inisialize of oobinline.
(fhandler_socket_inet::recv_internal): Make the handling of OOB data
as consistent with POSIX as possible. Add simulation of inline mode
for OOB data as a workaround for broken winsock behaviour.
(fhandler_socket_inet::setsockopt): Ditto.
(fhandler_socket_inet::getsockopt): Ditto.
(fhandler_socket_wsock::ioctl): Fix return value of SIOCATMARK command.
The return value of SIOCATMARK of winsock is almost opposite to
expectation.
* fhandler_socket_local.cc (fhandler_socket_local::recv_internal):
Make the handling of OOB data as consistent with POSIX as possible.
Add simulation of inline mode for OOB data as a workaround for broken
winsock behaviour.
(fhandler_socket_local::setsockopt): Ditto.
(fhandler_socket_local::getsockopt): Ditto.
This fixes the issue reported in following post.
https://cygwin.com/ml/cygwin/2018-06/msg00143.html
---
winsup/cygwin/fhandler.h | 1 +
winsup/cygwin/fhandler_socket_inet.cc | 92 +++++++++++++++++++++++++-
winsup/cygwin/fhandler_socket_local.cc | 80 +++++++++++++++++++++-
3 files changed, 167 insertions(+), 6 deletions(-)
diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index 2ec460a37..8222fb835 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -601,6 +601,7 @@ class fhandler_socket_wsock: public fhandler_socket
wsa_event *wsock_events;
HANDLE wsock_mtx;
HANDLE wsock_evt;
+ bool oobinline; /* True if option SO_OOBINLINE is set */
bool init_events ();
int wait_for_events (const long event_mask, const DWORD flags);
void release_events ();
diff --git a/winsup/cygwin/fhandler_socket_inet.cc b/winsup/cygwin/fhandler_socket_inet.cc
index db301f354..24baf9c89 100644
--- a/winsup/cygwin/fhandler_socket_inet.cc
+++ b/winsup/cygwin/fhandler_socket_inet.cc
@@ -201,6 +201,7 @@ fhandler_socket_wsock::fhandler_socket_wsock () :
wsock_events (NULL),
wsock_mtx (NULL),
wsock_evt (NULL),
+ oobinline (false),
status (),
prot_info_ptr (NULL)
{
@@ -1044,10 +1045,11 @@ fhandler_socket_inet::recv_internal (LPWSAMSG wsamsg, bool use_recvmsg)
{
ssize_t res = 0;
DWORD ret = 0, wret;
- int evt_mask = FD_READ | ((wsamsg->dwFlags & MSG_OOB) ? FD_OOB : 0);
+ int evt_mask = (wsamsg->dwFlags & MSG_OOB) ? FD_OOB : FD_READ;
LPWSABUF &wsabuf = wsamsg->lpBuffers;
ULONG &wsacnt = wsamsg->dwBufferCount;
static NO_COPY LPFN_WSARECVMSG WSARecvMsg;
+ bool read_oob = false;
/* CV 2014-10-26: Do not check for the connect_state at this point. In
certain scenarios there's no way to check the connect state reliably.
@@ -1086,12 +1088,64 @@ fhandler_socket_inet::recv_internal (LPWSAMSG wsamsg, bool use_recvmsg)
waitall = false;
}
+ /* recv() returns EINVAL if MSG_OOB flag is set in inline mode. */
+ if (oobinline && (wsamsg->dwFlags & MSG_OOB))
+ {
+ set_errno (EINVAL);
+ return SOCKET_ERROR;
+ }
+
+ /* Check whether OOB data is ready or not */
+ if (get_socket_type () == SOCK_STREAM)
+ if ((wsamsg->dwFlags & MSG_OOB) || oobinline)
+ {
+ u_long atmark = 0;
+#ifdef __x86_64__
+ /* SIOCATMARK = _IOR('s',7,u_long) */
+ int err = ::ioctlsocket (get_socket (), _IOR('s',7,u_long), &atmark);
+#else
+ int err = ::ioctlsocket (get_socket (), SIOCATMARK, &atmark);
+#endif
+ if (err)
+ {
+ set_winsock_errno ();
+ return SOCKET_ERROR;
+ }
+ /* If there is no OOB data, recv() with MSG_OOB returns EINVAL.
+ Note: The return value of SIOCATMARK in non-inline mode of
+ winsock is FALSE if OOB data exists, TRUE otherwise. */
+ if (atmark && (wsamsg->dwFlags & MSG_OOB))
+ {
+ /* No OOB data */
+ set_errno (EINVAL);
+ return SOCKET_ERROR;
+ }
+ /* Inline mode for oub-of-band (OOB) data of winsock is
+ completely broken. That is, SIOCATMARK always returns
+ TRUE in inline mode. Due to this problem, application
+ cannot determine OOB data at all. Therefore the behavior
+ of a socket with SO_OOBINLINE set is simulated using
+ a socket with SO_OOBINLINE not set. In this fake inline
+ mode, the order of the OOB and non-OOB data is not
+ preserved. OOB data is read before non-OOB data sent
+ prior to the OOB data. However, this is most likely
+ not a problem in most cases. */
+ /* If there is OOB data, read OOB data using MSG_OOB in
+ fake inline mode. */
+ if (!atmark && oobinline)
+ {
+ read_oob = true;
+ evt_mask = FD_OOB;
+ }
+ }
+
/* Note: Don't call WSARecvFrom(MSG_PEEK) without actually having data
waiting in the buffers, otherwise the event handling gets messed up
for some reason. */
while (!(res = wait_for_events (evt_mask | FD_CLOSE, wait_flags))
|| saw_shutdown_read ())
{
+ DWORD dwFlags = wsamsg->dwFlags | (read_oob ? MSG_OOB : 0);
if (use_recvmsg)
res = WSARecvMsg (get_socket (), wsamsg, &wret, NULL, NULL);
/* This is working around a really weird problem in WinSock.
@@ -1113,11 +1167,11 @@ fhandler_socket_inet::recv_internal (LPWSAMSG wsamsg, bool use_recvmsg)
namelen is a valid pointer while name is NULL. Both parameters are
ignored for TCP sockets, so this only occurs when using UDP socket. */
else if (!wsamsg->name || get_socket_type () == SOCK_STREAM)
- res = WSARecv (get_socket (), wsabuf, wsacnt, &wret, &wsamsg->dwFlags,
+ res = WSARecv (get_socket (), wsabuf, wsacnt, &wret, &dwFlags,
NULL, NULL);
else
res = WSARecvFrom (get_socket (), wsabuf, wsacnt, &wret,
- &wsamsg->dwFlags, wsamsg->name, &wsamsg->namelen,
+ &dwFlags, wsamsg->name, &wsamsg->namelen,
NULL, NULL);
if (!res)
{
@@ -1561,6 +1615,23 @@ fhandler_socket_inet::setsockopt (int level, int optname, const void *optval,
set_errno (EDOM);
return ret;
+ case SO_OOBINLINE:
+ /* Inline mode for oub-of-band (OOB) data of winsock is
+ completely broken. That is, SIOCATMARK always returns
+ TRUE in inline mode. Due to this problem, application
+ cannot determine OOB data at all. Therefore the behavior
+ of a socket with SO_OOBINLINE set is simulated using
+ a socket with SO_OOBINLINE not set. In this fake inline
+ mode, the order of the OOB and non-OOB data is not
+ preserved. OOB data is read before non-OOB data sent
+ prior to the OOB data. However, this is most likely
+ not a problem in most cases. */
+ /* Here, instead of actually setting inline mode, simply
+ set the variable oobinline. */
+ oobinline = *(int *) optval ? true : false;
+ ignore = true;
+ break;
+
default:
break;
}
@@ -1713,6 +1784,10 @@ fhandler_socket_inet::getsockopt (int level, int optname, const void *optval,
return 0;
}
+ case SO_OOBINLINE:
+ *(int *) optval = oobinline ? 1 : 0;
+ return 0;
+
default:
break;
}
@@ -1850,6 +1925,17 @@ fhandler_socket_wsock::ioctl (unsigned int cmd, void *p)
}
else
res = ::ioctlsocket (get_socket (), cmd, (u_long *) p);
+ /* In winsock, the return value of SIOCATMARK is FALSE if
+ OOB data exists, TRUE otherwise. This is almost opposite
+ to expectation. */
+#ifdef __x86_64__
+ /* SIOCATMARK = _IOR('s',7,u_long) */
+ if (cmd == _IOR('s',7,u_long) && !res)
+ *(u_long *)p = !*(u_long *)p;
+#else
+ if (cmd == SIOCATMARK && !res)
+ *(u_long *)p = !*(u_long *)p;
+#endif
break;
default:
res = fhandler_socket::ioctl (cmd, p);
diff --git a/winsup/cygwin/fhandler_socket_local.cc b/winsup/cygwin/fhandler_socket_local.cc
index 90d8d5aa5..7f776167a 100644
--- a/winsup/cygwin/fhandler_socket_local.cc
+++ b/winsup/cygwin/fhandler_socket_local.cc
@@ -1065,11 +1065,12 @@ fhandler_socket_local::recv_internal (LPWSAMSG wsamsg, bool use_recvmsg)
{
ssize_t res = 0;
DWORD ret = 0, wret;
- int evt_mask = FD_READ | ((wsamsg->dwFlags & MSG_OOB) ? FD_OOB : 0);
+ int evt_mask = (wsamsg->dwFlags & MSG_OOB) ? FD_OOB : FD_READ;
LPWSABUF &wsabuf = wsamsg->lpBuffers;
ULONG &wsacnt = wsamsg->dwBufferCount;
static NO_COPY LPFN_WSARECVMSG WSARecvMsg;
int orig_namelen = wsamsg->namelen;
+ bool read_oob = false;
/* CV 2014-10-26: Do not check for the connect_state at this point. In
certain scenarios there's no way to check the connect state reliably.
@@ -1108,12 +1109,65 @@ fhandler_socket_local::recv_internal (LPWSAMSG wsamsg, bool use_recvmsg)
waitall = false;
}
+ /* recv() returns EINVAL if MSG_OOB flag is set in inline mode. */
+ if (oobinline && (wsamsg->dwFlags & MSG_OOB))
+ {
+ set_errno (EINVAL);
+ return SOCKET_ERROR;
+ }
+
+ /* Check whether OOB data is ready or not */
+ if (get_socket_type () == SOCK_STREAM)
+ if ((wsamsg->dwFlags & MSG_OOB) || oobinline)
+ {
+ u_long atmark = 0;
+ /* SIOCATMARK = _IOR('s',7,u_long) */
+#ifdef __x86_64__
+ /* SIOCATMARK = _IOR('s',7,u_long) */
+ int err = ::ioctlsocket (get_socket (), _IOR('s',7,u_long), &atmark);
+#else
+ int err = ::ioctlsocket (get_socket (), SIOCATMARK, &atmark);
+#endif
+ if (err)
+ {
+ set_winsock_errno ();
+ return SOCKET_ERROR;
+ }
+ /* If there is no OOB data, recv() with MSG_OOB returns EINVAL.
+ Note: The return value of SIOCATMARK in non-inline mode of
+ winsock is FALSE if OOB data exists, TRUE otherwise. */
+ if (atmark && (wsamsg->dwFlags & MSG_OOB))
+ {
+ /* No OOB data */
+ set_errno (EINVAL);
+ return SOCKET_ERROR;
+ }
+ /* Inline mode for oub-of-band (OOB) data of winsock is
+ completely broken. That is, SIOCATMARK always returns
+ TRUE in inline mode. Due to this problem, application
+ cannot determine OOB data at all. Therefore the behavior
+ of a socket with SO_OOBINLINE set is simulated using
+ a socket with SO_OOBINLINE not set. In this fake inline
+ mode, the order of the OOB and non-OOB data is not
+ preserved. OOB data is read before non-OOB data sent
+ prior to the OOB data. However, this is most likely
+ not a problem in most cases. */
+ /* If there is OOB data, read OOB data using MSG_OOB in
+ fake inline mode. */
+ if (!atmark && oobinline)
+ {
+ read_oob = true;
+ evt_mask = FD_OOB;
+ }
+ }
+
/* Note: Don't call WSARecvFrom(MSG_PEEK) without actually having data
waiting in the buffers, otherwise the event handling gets messed up
for some reason. */
while (!(res = wait_for_events (evt_mask | FD_CLOSE, wait_flags))
|| saw_shutdown_read ())
{
+ DWORD dwFlags = wsamsg->dwFlags | (read_oob ? MSG_OOB : 0);
if (use_recvmsg)
res = WSARecvMsg (get_socket (), wsamsg, &wret, NULL, NULL);
/* This is working around a really weird problem in WinSock.
@@ -1135,11 +1189,11 @@ fhandler_socket_local::recv_internal (LPWSAMSG wsamsg, bool use_recvmsg)
namelen is a valid pointer while name is NULL. Both parameters are
ignored for TCP sockets, so this only occurs when using UDP socket. */
else if (!wsamsg->name || get_socket_type () == SOCK_STREAM)
- res = WSARecv (get_socket (), wsabuf, wsacnt, &wret, &wsamsg->dwFlags,
+ res = WSARecv (get_socket (), wsabuf, wsacnt, &wret, &dwFlags,
NULL, NULL);
else
res = WSARecvFrom (get_socket (), wsabuf, wsacnt, &wret,
- &wsamsg->dwFlags, wsamsg->name, &wsamsg->namelen,
+ &dwFlags, wsamsg->name, &wsamsg->namelen,
NULL, NULL);
if (!res)
{
@@ -1396,6 +1450,22 @@ fhandler_socket_local::setsockopt (int level, int optname, const void *optval,
case SO_SNDLOWAT:
break;
+ case SO_OOBINLINE:
+ /* Inline mode for oub-of-band (OOB) data of winsock is
+ completely broken. That is, SIOCATMARK always returns
+ TRUE in inline mode. Due to this problem, application
+ cannot determine OOB data at all. Therefore the behavior
+ of a socket with SO_OOBINLINE set is simulated using
+ a socket with SO_OOBINLINE not set. In this fake inline
+ mode, the order of the OOB and non-OOB data is not
+ preserved. OOB data is read before non-OOB data sent
+ prior to the OOB data. However, this is most likely
+ not a problem in most cases. */
+ /* Here, instead of actually setting inline mode, simply
+ set the variable oobinline. */
+ oobinline = *(int *) optval ? true : false;
+ return 0;
+
default:
/* AF_LOCAL sockets simply ignore all other SOL_SOCKET options. */
return 0;
@@ -1538,6 +1608,10 @@ fhandler_socket_local::getsockopt (int level, int optname, const void *optval,
return 0;
}
+ case SO_OOBINLINE:
+ *(int *) optval = oobinline ? 1 : 0;
+ return 0;
+
default:
{
unsigned int *val = (unsigned int *) optval;
--
2.17.0
[-- Attachment #3: Type: text/plain, Size: 219 bytes --]
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Problems of AF_INET domain socket regarding out-of-band data.
2018-06-21 1:35 ` Takashi Yano
@ 2018-06-21 14:05 ` Corinna Vinschen
0 siblings, 0 replies; 3+ messages in thread
From: Corinna Vinschen @ 2018-06-21 14:05 UTC (permalink / raw)
To: cygwin
[-- Attachment #1: Type: text/plain, Size: 3064 bytes --]
Hi Takashi,
(just a sidenote: it would be nice if you would send your patches
to the cygwin-patches mailing list)
On Jun 20 22:18, Takashi Yano wrote:
> Hi Corinna,
>
> On Wed, 13 Jun 2018 22:48:58 +0900
> Takashi Yano wrote:
> > 1. recv() with MSG_OOB flag eats normal data if no OOB data
> > is sent yet.
> >
> > 2. Calling recv() with MSG_OOB flag is blocked if no OOB data
> > is sent yet.
> >
> > 3. Calling recv() without MSG_OOB flag after receiving OOB data
> > is blocked even if received data exist in buffer.
>
> I looked into these problems and found these are due to bug of
> cygwin1.dll.
>
> Problem 1:
> If recv() is called with MSG_OOB, in fhandler_socket_inet::
> recv_internal(), wsamsg->dwFlags with MSG_OOB flag set is passed
> to WSARecv() and this fails because no OOB data exists. At this time,
> wsamsg-> dwFlags is modified by WSARecv() so that it does not have
> the MSG_OOB flag. Then, WSARecv() is called again without MSG_OOB
> flag in while loop. At this time, normal data is read and returned.
>
> Problem 2:
> In fhandler_socket_inet::recv_internal(), wait_for_events() is
> called. This blocks the call until OOB data arrives.
>
> Problem 3:
> If recv() is called with MSG_OOB flag set, fhandler_socket_inet::
> recv_internal() calls wait_for_events() with both FD_OOB and
> FD_READ. If both OOB data and normal data already arrived,
> not only the event of FD_OOB but also the event of FD_READ are
> reset to non signaled state. I'm not sure where the signal is
> reset, though.
>
> Moreover, return value of ioctl command SIOCATMARK of winsock
> is not as expected. In winsock, SIOCATMARK returns TRUE if no
> OOB data exists, FALSE otherwise. This is almost opposite to
> expectation.
>
> Furthermore, inline mode (SO_OOBINLINE) of winsock is completely
> broken. If SO_OOBINLINE is set, SIOATMARK always returns TRUE.
> This means application cannot determine OOB data at all in inline
> mode.
>
> To solve these problems, I made a patch attached.
>
> Could you please have a look?
Thanks for the patch. I had a look and your implemantation looks good
to me. Two points:
- The minor point: There's a typo "oub-of-band" in the comment
handling the SO_OOBINLINE ioctl.
- The major point: Now that INET and LOCAL sockets are handled
separately, we may want to follow Linux' lead:
"UNIX domain sockets do not support the transmission of out-of-band data
(the MSG_OOB flag for send(2) and recv(2))" (quote from `man 7 unix')
If I ever get around to finish the new AF_UNIX implemantation it won't
support OOB anyway. For the time being, we may want to disable OOB in
fhandler_socket_local already, so, rather than duplicating the changes
to AF_INET, we could simply disable OOB handling in
fhandler_socket_local entirely. Care to do that?
Thanks,
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
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2018-06-13 15:02 Problems of AF_INET domain socket regarding out-of-band data Takashi Yano
2018-06-21 1:35 ` Takashi Yano
2018-06-21 14:05 ` Corinna Vinschen
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