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putty/windows/winhandl.c

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C
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/*
* winhandl.c: Module to give Windows front ends the general
* ability to deal with consoles, pipes, serial ports, or any other
* type of data stream accessed through a Windows API HANDLE rather
* than a WinSock SOCKET.
*
* We do this by spawning a subthread to continuously try to read
* from the handle. Every time a read successfully returns some
* data, the subthread sets an event object which is picked up by
* the main thread, and the main thread then sets an event in
* return to instruct the subthread to resume reading.
*
* Output works precisely the other way round, in a second
* subthread. The output subthread should not be attempting to
* write all the time, because it hasn't always got data _to_
* write; so the output thread waits for an event object notifying
* it to _attempt_ a write, and then it sets an event in return
* when one completes.
*
* (It's terribly annoying having to spawn a subthread for each
* direction of each handle. Technically it isn't necessary for
* serial ports, since we could use overlapped I/O within the main
* thread and wait directly on the event objects in the OVERLAPPED
* structures. However, we can't use this trick for some types of
* file handle at all - for some reason Windows restricts use of
* OVERLAPPED to files which were opened with the overlapped flag -
* and so we must use threads for those. This being the case, it's
* simplest just to use threads for everything rather than trying
* to keep track of multiple completely separate mechanisms.)
*/
#include <assert.h>
#include "putty.h"
/* ----------------------------------------------------------------------
* Generic definitions.
*/
/*
* Maximum amount of backlog we will allow to build up on an input
* handle before we stop reading from it.
*/
#define MAX_BACKLOG 32768
struct handle_generic {
/*
* Initial fields common to both handle_input and handle_output
* structures.
*
* The three HANDLEs are set up at initialisation time and are
* thereafter read-only to both main thread and subthread.
* `moribund' is only used by the main thread; `done' is
* written by the main thread before signalling to the
* subthread. `defunct' and `busy' are used only by the main
* thread.
*/
HANDLE h; /* the handle itself */
HANDLE ev_to_main; /* event used to signal main thread */
HANDLE ev_from_main; /* event used to signal back to us */
bool moribund; /* are we going to kill this soon? */
bool done; /* request subthread to terminate */
bool defunct; /* has the subthread already gone? */
bool busy; /* operation currently in progress? */
void *privdata; /* for client to remember who they are */
};
typedef enum { HT_INPUT, HT_OUTPUT, HT_FOREIGN } HandleType;
/* ----------------------------------------------------------------------
* Input threads.
*/
/*
* Data required by an input thread.
*/
struct handle_input {
/*
* Copy of the handle_generic structure.
*/
HANDLE h; /* the handle itself */
HANDLE ev_to_main; /* event used to signal main thread */
HANDLE ev_from_main; /* event used to signal back to us */
bool moribund; /* are we going to kill this soon? */
bool done; /* request subthread to terminate */
bool defunct; /* has the subthread already gone? */
bool busy; /* operation currently in progress? */
void *privdata; /* for client to remember who they are */
/*
* Data set at initialisation and then read-only.
*/
int flags;
/*
* Data set by the input thread before signalling ev_to_main,
* and read by the main thread after receiving that signal.
*/
char buffer[4096]; /* the data read from the handle */
DWORD len; /* how much data that was */
int readerr; /* lets us know about read errors */
/*
* Callback function called by this module when data arrives on
* an input handle.
*/
handle_inputfn_t gotdata;
};
/*
* The actual thread procedure for an input thread.
*/
static DWORD WINAPI handle_input_threadfunc(void *param)
{
struct handle_input *ctx = (struct handle_input *) param;
OVERLAPPED ovl, *povl;
HANDLE oev;
bool readret, finished;
int readlen;
if (ctx->flags & HANDLE_FLAG_OVERLAPPED) {
povl = &ovl;
oev = CreateEvent(NULL, true, false, NULL);
} else {
povl = NULL;
}
if (ctx->flags & HANDLE_FLAG_UNITBUFFER)
readlen = 1;
else
readlen = sizeof(ctx->buffer);
while (1) {
if (povl) {
memset(povl, 0, sizeof(OVERLAPPED));
povl->hEvent = oev;
}
readret = ReadFile(ctx->h, ctx->buffer,readlen, &ctx->len, povl);
if (!readret)
ctx->readerr = GetLastError();
else
ctx->readerr = 0;
if (povl && !readret && ctx->readerr == ERROR_IO_PENDING) {
WaitForSingleObject(povl->hEvent, INFINITE);
readret = GetOverlappedResult(ctx->h, povl, &ctx->len, false);
if (!readret)
ctx->readerr = GetLastError();
else
ctx->readerr = 0;
}
if (!readret) {
/*
* Windows apparently sends ERROR_BROKEN_PIPE when a
* pipe we're reading from is closed normally from the
* writing end. This is ludicrous; if that situation
* isn't a natural EOF, _nothing_ is. So if we get that
* particular error, we pretend it's EOF.
*/
if (ctx->readerr == ERROR_BROKEN_PIPE)
ctx->readerr = 0;
ctx->len = 0;
}
if (readret && ctx->len == 0 &&
(ctx->flags & HANDLE_FLAG_IGNOREEOF))
continue;
/*
* If we just set ctx->len to 0, that means the read operation
* has returned end-of-file. Telling that to the main thread
* will cause it to set its 'defunct' flag and dispose of the
* handle structure at the next opportunity, in which case we
* mustn't touch ctx at all after the SetEvent. (Hence we do
* even _this_ check before the SetEvent.)
*/
finished = (ctx->len == 0);
SetEvent(ctx->ev_to_main);
if (finished)
break;
WaitForSingleObject(ctx->ev_from_main, INFINITE);
if (ctx->done) {
/*
* The main thread has asked us to shut down. Send back an
* event indicating that we've done so. Hereafter we must
* not touch ctx at all, because the main thread might
* have freed it.
*/
SetEvent(ctx->ev_to_main);
break;
}
}
if (povl)
CloseHandle(oev);
return 0;
}
/*
* This is called after a succcessful read, or from the
* `unthrottle' function. It decides whether or not to begin a new
* read operation.
*/
static void handle_throttle(struct handle_input *ctx, int backlog)
{
if (ctx->defunct)
return;
/*
* If there's a read operation already in progress, do nothing:
* when that completes, we'll come back here and be in a
* position to make a better decision.
*/
if (ctx->busy)
return;
/*
* Otherwise, we must decide whether to start a new read based
* on the size of the backlog.
*/
if (backlog < MAX_BACKLOG) {
SetEvent(ctx->ev_from_main);
ctx->busy = true;
}
}
/* ----------------------------------------------------------------------
* Output threads.
*/
/*
* Data required by an output thread.
*/
struct handle_output {
/*
* Copy of the handle_generic structure.
*/
HANDLE h; /* the handle itself */
HANDLE ev_to_main; /* event used to signal main thread */
HANDLE ev_from_main; /* event used to signal back to us */
bool moribund; /* are we going to kill this soon? */
bool done; /* request subthread to terminate */
bool defunct; /* has the subthread already gone? */
bool busy; /* operation currently in progress? */
void *privdata; /* for client to remember who they are */
/*
* Data set at initialisation and then read-only.
*/
int flags;
/*
* Data set by the main thread before signalling ev_from_main,
* and read by the input thread after receiving that signal.
*/
const char *buffer; /* the data to write */
DWORD len; /* how much data there is */
/*
* Data set by the input thread before signalling ev_to_main,
* and read by the main thread after receiving that signal.
*/
DWORD lenwritten; /* how much data we actually wrote */
int writeerr; /* return value from WriteFile */
/*
* Data only ever read or written by the main thread.
*/
bufchain queued_data; /* data still waiting to be written */
enum { EOF_NO, EOF_PENDING, EOF_SENT } outgoingeof;
/*
* Callback function called when the backlog in the bufchain
* drops.
*/
handle_outputfn_t sentdata;
};
static DWORD WINAPI handle_output_threadfunc(void *param)
{
struct handle_output *ctx = (struct handle_output *) param;
OVERLAPPED ovl, *povl;
HANDLE oev;
bool writeret;
if (ctx->flags & HANDLE_FLAG_OVERLAPPED) {
povl = &ovl;
oev = CreateEvent(NULL, true, false, NULL);
} else {
povl = NULL;
}
while (1) {
WaitForSingleObject(ctx->ev_from_main, INFINITE);
if (ctx->done) {
/*
* The main thread has asked us to shut down. Send back an
* event indicating that we've done so. Hereafter we must
* not touch ctx at all, because the main thread might
* have freed it.
*/
SetEvent(ctx->ev_to_main);
break;
}
if (povl) {
memset(povl, 0, sizeof(OVERLAPPED));
povl->hEvent = oev;
}
writeret = WriteFile(ctx->h, ctx->buffer, ctx->len,
&ctx->lenwritten, povl);
if (!writeret)
ctx->writeerr = GetLastError();
else
ctx->writeerr = 0;
if (povl && !writeret && GetLastError() == ERROR_IO_PENDING) {
writeret = GetOverlappedResult(ctx->h, povl,
&ctx->lenwritten, true);
if (!writeret)
ctx->writeerr = GetLastError();
else
ctx->writeerr = 0;
}
SetEvent(ctx->ev_to_main);
if (!writeret) {
/*
* The write operation has suffered an error. Telling that
* to the main thread will cause it to set its 'defunct'
* flag and dispose of the handle structure at the next
* opportunity, so we must not touch ctx at all after
* this.
*/
break;
}
}
if (povl)
CloseHandle(oev);
return 0;
}
static void handle_try_output(struct handle_output *ctx)
{
if (!ctx->busy && bufchain_size(&ctx->queued_data)) {
ptrlen data = bufchain_prefix(&ctx->queued_data);
ctx->buffer = data.ptr;
ctx->len = min(data.len, ~(DWORD)0);
SetEvent(ctx->ev_from_main);
ctx->busy = true;
} else if (!ctx->busy && bufchain_size(&ctx->queued_data) == 0 &&
ctx->outgoingeof == EOF_PENDING) {
CloseHandle(ctx->h);
ctx->h = INVALID_HANDLE_VALUE;
ctx->outgoingeof = EOF_SENT;
}
}
/* ----------------------------------------------------------------------
* 'Foreign events'. These are handle structures which just contain a
* single event object passed to us by another module such as
* winnps.c, so that they can make use of our handle_get_events /
* handle_got_event mechanism for communicating with application main
* loops.
*/
struct handle_foreign {
/*
* Copy of the handle_generic structure.
*/
HANDLE h; /* the handle itself */
HANDLE ev_to_main; /* event used to signal main thread */
HANDLE ev_from_main; /* event used to signal back to us */
bool moribund; /* are we going to kill this soon? */
bool done; /* request subthread to terminate */
bool defunct; /* has the subthread already gone? */
bool busy; /* operation currently in progress? */
void *privdata; /* for client to remember who they are */
/*
* Our own data, just consisting of knowledge of who to call back.
*/
void (*callback)(void *);
void *ctx;
};
/* ----------------------------------------------------------------------
* Unified code handling both input and output threads.
*/
struct handle {
HandleType type;
union {
struct handle_generic g;
struct handle_input i;
struct handle_output o;
struct handle_foreign f;
} u;
};
static tree234 *handles_by_evtomain;
static int handle_cmp_evtomain(void *av, void *bv)
{
struct handle *a = (struct handle *)av;
struct handle *b = (struct handle *)bv;
if ((uintptr_t)a->u.g.ev_to_main < (uintptr_t)b->u.g.ev_to_main)
return -1;
else if ((uintptr_t)a->u.g.ev_to_main > (uintptr_t)b->u.g.ev_to_main)
return +1;
else
return 0;
}
static int handle_find_evtomain(void *av, void *bv)
{
HANDLE *a = (HANDLE *)av;
struct handle *b = (struct handle *)bv;
if ((uintptr_t)*a < (uintptr_t)b->u.g.ev_to_main)
return -1;
else if ((uintptr_t)*a > (uintptr_t)b->u.g.ev_to_main)
return +1;
else
return 0;
}
struct handle *handle_input_new(HANDLE handle, handle_inputfn_t gotdata,
void *privdata, int flags)
{
struct handle *h = snew(struct handle);
DWORD in_threadid; /* required for Win9x */
h->type = HT_INPUT;
h->u.i.h = handle;
h->u.i.ev_to_main = CreateEvent(NULL, false, false, NULL);
h->u.i.ev_from_main = CreateEvent(NULL, false, false, NULL);
h->u.i.gotdata = gotdata;
h->u.i.defunct = false;
h->u.i.moribund = false;
h->u.i.done = false;
h->u.i.privdata = privdata;
h->u.i.flags = flags;
if (!handles_by_evtomain)
handles_by_evtomain = newtree234(handle_cmp_evtomain);
add234(handles_by_evtomain, h);
CreateThread(NULL, 0, handle_input_threadfunc,
&h->u.i, 0, &in_threadid);
h->u.i.busy = true;
return h;
}
struct handle *handle_output_new(HANDLE handle, handle_outputfn_t sentdata,
void *privdata, int flags)
{
struct handle *h = snew(struct handle);
DWORD out_threadid; /* required for Win9x */
h->type = HT_OUTPUT;
h->u.o.h = handle;
h->u.o.ev_to_main = CreateEvent(NULL, false, false, NULL);
h->u.o.ev_from_main = CreateEvent(NULL, false, false, NULL);
h->u.o.busy = false;
h->u.o.defunct = false;
h->u.o.moribund = false;
h->u.o.done = false;
h->u.o.privdata = privdata;
bufchain_init(&h->u.o.queued_data);
h->u.o.outgoingeof = EOF_NO;
h->u.o.sentdata = sentdata;
h->u.o.flags = flags;
if (!handles_by_evtomain)
handles_by_evtomain = newtree234(handle_cmp_evtomain);
add234(handles_by_evtomain, h);
CreateThread(NULL, 0, handle_output_threadfunc,
&h->u.o, 0, &out_threadid);
return h;
}
struct handle *handle_add_foreign_event(HANDLE event,
void (*callback)(void *), void *ctx)
{
struct handle *h = snew(struct handle);
h->type = HT_FOREIGN;
h->u.f.h = INVALID_HANDLE_VALUE;
h->u.f.ev_to_main = event;
h->u.f.ev_from_main = INVALID_HANDLE_VALUE;
h->u.f.defunct = true; /* we have no thread in the first place */
h->u.f.moribund = false;
h->u.f.done = false;
h->u.f.privdata = NULL;
h->u.f.callback = callback;
h->u.f.ctx = ctx;
h->u.f.busy = true;
if (!handles_by_evtomain)
handles_by_evtomain = newtree234(handle_cmp_evtomain);
add234(handles_by_evtomain, h);
return h;
}
size_t handle_write(struct handle *h, const void *data, size_t len)
{
assert(h->type == HT_OUTPUT);
assert(h->u.o.outgoingeof == EOF_NO);
bufchain_add(&h->u.o.queued_data, data, len);
handle_try_output(&h->u.o);
return bufchain_size(&h->u.o.queued_data);
}
void handle_write_eof(struct handle *h)
{
/*
* This function is called when we want to proactively send an
* end-of-file notification on the handle. We can only do this by
* actually closing the handle - so never call this on a
* bidirectional handle if we're still interested in its incoming
* direction!
*/
assert(h->type == HT_OUTPUT);
if (h->u.o.outgoingeof == EOF_NO) {
h->u.o.outgoingeof = EOF_PENDING;
handle_try_output(&h->u.o);
}
}
HANDLE *handle_get_events(int *nevents)
{
HANDLE *ret;
struct handle *h;
int i;
size_t n, size;
/*
* Go through our tree counting the handle objects currently
* engaged in useful activity.
*/
ret = NULL;
n = size = 0;
if (handles_by_evtomain) {
for (i = 0; (h = index234(handles_by_evtomain, i)) != NULL; i++) {
if (h->u.g.busy) {
sgrowarray(ret, size, n);
ret[n++] = h->u.g.ev_to_main;
}
}
}
*nevents = n;
return ret;
}
static void handle_destroy(struct handle *h)
{
if (h->type == HT_OUTPUT)
bufchain_clear(&h->u.o.queued_data);
CloseHandle(h->u.g.ev_from_main);
CloseHandle(h->u.g.ev_to_main);
del234(handles_by_evtomain, h);
sfree(h);
}
void handle_free(struct handle *h)
{
assert(h && !h->u.g.moribund);
if (h->u.g.busy && h->type != HT_FOREIGN) {
/*
* If the handle is currently busy, we cannot immediately free
* it, because its subthread is in the middle of something.
* (Exception: foreign handles don't have a subthread.)
*
* Instead we must wait until it's finished its current
* operation, because otherwise the subthread will write to
* invalid memory after we free its context from under it. So
* we set the moribund flag, which will be noticed next time
* an operation completes.
*/
h->u.g.moribund = true;
} else if (h->u.g.defunct) {
/*
* There isn't even a subthread; we can go straight to
* handle_destroy.
*/
handle_destroy(h);
} else {
/*
* The subthread is alive but not busy, so we now signal it
* to die. Set the moribund flag to indicate that it will
* want destroying after that.
*/
h->u.g.moribund = true;
h->u.g.done = true;
h->u.g.busy = true;
SetEvent(h->u.g.ev_from_main);
}
}
void handle_got_event(HANDLE event)
{
struct handle *h;
assert(handles_by_evtomain);
h = find234(handles_by_evtomain, &event, handle_find_evtomain);
if (!h) {
/*
* This isn't an error condition. If two or more event
* objects were signalled during the same select operation,
* and processing of the first caused the second handle to
* be closed, then it will sometimes happen that we receive
* an event notification here for a handle which is already
* deceased. In that situation we simply do nothing.
*/
return;
}
if (h->u.g.moribund) {
/*
* A moribund handle is one which we have either already
* signalled to die, or are waiting until its current I/O op
* completes to do so. Either way, it's treated as already
* dead from the external user's point of view, so we ignore
* the actual I/O result. We just signal the thread to die if
* we haven't yet done so, or destroy the handle if not.
*/
if (h->u.g.done) {
handle_destroy(h);
} else {
h->u.g.done = true;
h->u.g.busy = true;
SetEvent(h->u.g.ev_from_main);
}
return;
}
switch (h->type) {
int backlog;
case HT_INPUT:
h->u.i.busy = false;
/*
* A signal on an input handle means data has arrived.
*/
if (h->u.i.len == 0) {
/*
* EOF, or (nearly equivalently) read error.
*/
h->u.i.defunct = true;
h->u.i.gotdata(h, NULL, 0, h->u.i.readerr);
} else {
backlog = h->u.i.gotdata(h, h->u.i.buffer, h->u.i.len, 0);
handle_throttle(&h->u.i, backlog);
}
break;
case HT_OUTPUT:
h->u.o.busy = false;
/*
* A signal on an output handle means we have completed a
* write. Call the callback to indicate that the output
* buffer size has decreased, or to indicate an error.
*/
if (h->u.o.writeerr) {
/*
* Write error. Send a negative value to the callback,
* and mark the thread as defunct (because the output
* thread is terminating by now).
*/
h->u.o.defunct = true;
h->u.o.sentdata(h, 0, h->u.o.writeerr);
} else {
bufchain_consume(&h->u.o.queued_data, h->u.o.lenwritten);
noise_ultralight(NOISE_SOURCE_IOLEN, h->u.o.lenwritten);
h->u.o.sentdata(h, bufchain_size(&h->u.o.queued_data), 0);
handle_try_output(&h->u.o);
}
break;
case HT_FOREIGN:
/* Just call the callback. */
h->u.f.callback(h->u.f.ctx);
break;
}
}
void handle_unthrottle(struct handle *h, size_t backlog)
{
assert(h->type == HT_INPUT);
handle_throttle(&h->u.i, backlog);
}
size_t handle_backlog(struct handle *h)
{
assert(h->type == HT_OUTPUT);
return bufchain_size(&h->u.o.queued_data);
}
void *handle_get_privdata(struct handle *h)
{
return h->u.g.privdata;
}
static void handle_sink_write(BinarySink *bs, const void *data, size_t len)
{
handle_sink *sink = BinarySink_DOWNCAST(bs, handle_sink);
handle_write(sink->h, data, len);
}
void handle_sink_init(handle_sink *sink, struct handle *h)
{
sink->h = h;
BinarySink_INIT(sink, handle_sink_write);
}
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