websockets: remodeled API to support 63 bit frame sizes

curl_ws_recv() now receives data to fill up the provided buffer, but can
return a partial fragment. The function now also get a pointer to a
curl_ws_frame struct with metadata that also mentions the offset and
total size of the fragment (of which you might be receiving a smaller
piece). This way, large incoming fragments will be "streamed" to the
application. When the curl_ws_frame struct field 'bytesleft' is 0, the
final fragment piece has been delivered.

curl_ws_recv() was also adjusted to work with a buffer size smaller than
the fragment size. (Possibly needless to say as the fragment size can
now be 63 bit large).

curl_ws_send() now supports sending a piece of a fragment, in a
streaming manner, in addition to sending the entire fragment in a single
call if it is small enough. To send a huge fragment, curl_ws_send() can
be used to send it in many small calls by first telling libcurl about
the total expected fragment size, and then send the payload in N number
of separate invokes and libcurl will stream those over the wire.

The struct curl_ws_meta() returns is now called 'curl_ws_frame' and it
has been extended with two new fields: *offset* and *bytesleft*. To help
describe the passed on data chunk when a fragment is delivered in many
smaller pieces.

The documentation has been updated accordingly.

Closes #9636

docs/libcurl/curl_ws_meta.3

@@ -29,19 +29,21 @@ curl_ws_meta - meta data WebSocket information
 .nf
 #include <curl/easy.h>
 
-struct curl_ws_metadata {
+struct curl_ws_frame {
-  int age;       /* zero */
+  int age;              /* zero */
-  int recvflags; /* See the CURLWS_* defines */
+  int flags;            /* See the CURLWS_* defines */
+  curl_off_t offset;    /* the offset of this data into the frame */
+  curl_off_t bytesleft; /* number of pending bytes left of the payload */
 };
 
-struct curl_ws_metadata *curl_ws_meta(CURL *curl);
+struct curl_ws_frame *curl_ws_meta(CURL *curl);
 .fi
 .SH DESCRIPTION
 This function call is EXPERIMENTAL.
 
 When the write callback (\fICURLOPT_WRITEFUNCTION(3)\fP) is invoked on
 received WebSocket traffic, \fIcurl_ws_meta(3)\fP can be called from within
-the callback to provide additional information about the data.
+the callback to provide additional information about the current frame.
 
 This function only works from within the callback, and only when receiving
 WebSocket data.
@@ -54,9 +56,30 @@ to the callback by libcurl itself, applications that want to use
 .SH "struct fields"
 .IP age
 This field specify the age of this struct. It is always zero for now.
-.IP recvflags
+.IP flags
-This is a bitmask with the exact same meaning as the \fBrecvflags\fP
+This is a bitmask with individual bits set that describes the WebSocket
-documented for \fIcurl_ws_recv(3)\fP.
+data. See the list below.
+.IP offset
+When this frame is a continuation of fragment data already delivered, this is
+the offset into the final fragment where this piece belongs.
+.IP bytesleft
+If this is not a complete fragment, the \fIbytesleft\fP field informs about
+how many additional bytes are expected to arrive before this fragment is
+complete.
+.SH FLAGS
+.IP CURLWS_TEXT
+The buffer contains text data. Note that this makes a difference to WebSocket
+but libcurl itself will not make any verification of the content or
+precautions that you actually receive valid UTF-8 content.
+.IP CURLWS_BINARY
+This is binary data.
+.IP CURLWS_CONT
+This is not the final fragment of the message, it implies that there will be
+another fragment coming as part of the same message.
+.IP CURLWS_CLOSE
+This transfer is now closed.
+.IP CURLWS_PING
+This as an incoming ping message, that expects a pong response.
 .SH EXAMPLE
 .nf
 
@@ -70,9 +93,9 @@ static size_t writecb(unsigned char *buffer,
                       size_t size, size_t nitems, void *p)
 {
   struct customdata *c = (struct customdata *)p;
-  struct curl_ws_metadata *m = curl_ws_meta(c->easy);
+  struct curl_ws_frame *m = curl_ws_meta(c->easy);
 
-  /* m->recvflags tells us about the traffic */
+  /* m->flags tells us about the traffic */
 }
 
 {
@@ -86,10 +109,10 @@ static size_t writecb(unsigned char *buffer,
 .SH AVAILABILITY
 Added in 7.86.0.
 .SH RETURN VALUE
-This function returns a pointer to a metadata struct with information that is
+This function returns a pointer to a \fIcurl_ws_frame\fP struct with
-valid for this specific callback invocation. If it cannot return this
+information that is valid for this specific callback invocation. If it cannot
-information, or if the function is called in the wrong context, it returns
+return this information, or if the function is called in the wrong context, it
-NULL.
+returns NULL.
 .SH "SEE ALSO"
 .BR curl_easy_setopt "(3), "
 .BR curl_easy_getinfo "(3), "

docs/libcurl/curl_ws_recv.3

@@ -30,28 +30,22 @@ curl_ws_recv - receive WebSocket data
 #include <curl/easy.h>
 
 CURLcode curl_ws_recv(CURL *curl, void *buffer, size_t buflen,
-                      size_t *recv, unsigned int *flags);
+                      size_t *recv, struct curl_ws_frame **meta);
 .fi
 .SH DESCRIPTION
 This function call is EXPERIMENTAL.
 
 Retrieves as much as possible of a received WebSocket data fragment into the
-\fBbuffer\fP, but not more than \fBbuflen\fP bytes. The provide
+\fBbuffer\fP, but not more than \fBbuflen\fP bytes. \fIrecv\fP is set to the
-\fIflags\fP argument gets bits set to help characterize the fragment.
+number of bytes actually stored.
-.SH FLAGS
+
-.IP CURLWS_TEXT
+If there is more fragment data to deliver than what fits in the provided
-The buffer contains text data. Note that this makes a difference to WebSocket
+\fIbuffer\fP, libcurl returns a full buffer and the application needs to call
-but libcurl itself will not make any verification of the content or
+this function again to continue draining the buffer.
-precautions that you actually receive valid UTF-8 content.
+
-.IP CURLWS_BINARY
+The \fImeta\fP pointer gets set to point to a \fIstruct curl_ws_frame\fP that
-This is binary data.
+contains information about the received data. See the \fIcurl_ws_meta(3)\fP
-.IP CURLWS_CONT
+for details on that struct.
-This is not the final fragment of the message, it implies that there will be
-another fragment coming as part of the same message.
-.IP CURLWS_CLOSE
-This transfer is now closed.
-.IP CURLWS_PING
-This as an incoming ping message, that expects a pong response.
 .SH EXAMPLE
 .nf
 

docs/libcurl/curl_ws_send.3

@@ -24,18 +24,31 @@
 .\"
 .TH curl_ws_send 3 "12 Jun 2022" "libcurl 7.85.0" "libcurl Manual"
 .SH NAME
-curl_ws_send - receive WebSocket data
+curl_ws_send - send WebSocket data
 .SH SYNOPSIS
 .nf
 #include <curl/easy.h>
 
 CURLcode curl_ws_send(CURL *curl, const void *buffer, size_t buflen,
-                      size_t *sent, unsigned int flags);
+                      size_t *sent, curl_off_t framesize,
+                      unsigned int flags);
 .fi
 .SH DESCRIPTION
 This function call is EXPERIMENTAL.
 
-Send the specific message fragment over the established WebSocket connection.
+Send the specific message fragment over an established WebSocket
+connection. The \fIbuffer\fP holds the data to send and it is \fIbuflen\fP
+number of payload bytes in that memory area.
+
+\fIsent\fP is returned as the number of payload bytes actually sent.
+
+To send a (huge) fragment using multiple calls with partial content per
+invoke, set the \fICURLWS_OFFSET\fP bit and the \fIframesize\fP argument as
+the total expected size for the first part, then set the \fICURLWS_OFFSET\fP
+with a zero \fItotalsize\fP for the following parts.
+
+If not sending a partial fragment or if this is raw mode, \fIframsize\fP
+should be set to zero.
 
 If \fBCURLWS_RAW_MODE\fP is enabled in \fICURLOPT_WS_OPTIONS(3)\fP, the
 \fBflags\fP argument should be set to 0.
@@ -47,8 +60,6 @@ but libcurl itself will not make any verification of the content or
 precautions that you actually send valid UTF-8 content.
 .IP CURLWS_BINARY
 This is binary data.
-.IP CURLWS_NOCOMPRESS
-No-op if there’s no compression anyway.
 .IP CURLWS_CONT
 This is not the final fragment of the message, which implies that there will
 be another fragment coming as part of the same message where this bit is not
@@ -59,6 +70,12 @@ Close this transfer.
 This as a ping.
 .IP CURLWS_PONG
 This as a pong.
+.IP CURLWS_OFFSET
+The provided data is only a partial fragment and there will be more in a
+following call to \fIcurl_ws_send()\fP. When sending only a piece of the
+fragment like this, the \fIframesize\fP must be provided with the total
+expected frame size in the first call and it needs to be zero in subsequent
+calls.
 .SH EXAMPLE
 .nf
 

docs/libcurl/symbols-in-versions

@@ -1111,7 +1111,7 @@ CURLWARNING                     7.66.0
 CURLWS_BINARY                   7.86.0
 CURLWS_CLOSE                    7.86.0
 CURLWS_CONT                     7.86.0
-CURLWS_NOCOMPRESS               7.86.0
+CURLWS_OFFSET                   7.86.0
 CURLWS_PING                     7.86.0
 CURLWS_PONG                     7.86.0
 CURLWS_RAW_MODE                 7.86.0

include/curl/websockets.h

@@ -28,12 +28,20 @@
 extern "C" {
 #endif
 
-/* generic in/out flag bits */
+struct curl_ws_frame {
+  int age;              /* zero */
+  int flags;            /* See the CURLWS_* defines */
+  curl_off_t offset;    /* the offset of this data into the frame */
+  curl_off_t bytesleft; /* number of pending bytes left of the payload */
+};
+
+/* flag bits */
 #define CURLWS_TEXT       (1<<0)
 #define CURLWS_BINARY     (1<<1)
 #define CURLWS_CONT       (1<<2)
 #define CURLWS_CLOSE      (1<<3)
 #define CURLWS_PING       (1<<4)
+#define CURLWS_OFFSET     (1<<5)
 
 /*
  * NAME curl_ws_recv()
@@ -44,10 +52,10 @@ extern "C" {
  * curl_easy_perform() with CURLOPT_CONNECT_ONLY option.
  */
 CURL_EXTERN CURLcode curl_ws_recv(CURL *curl, void *buffer, size_t buflen,
-                                  size_t *recv, unsigned int *recvflags);
+                                  size_t *recv,
+                                  struct curl_ws_frame **metap);
 
 /* sendflags for curl_ws_send() */
-#define CURLWS_NOCOMPRESS (1<<5)
 #define CURLWS_PONG       (1<<6)
 
 /*
@@ -60,17 +68,13 @@ CURL_EXTERN CURLcode curl_ws_recv(CURL *curl, void *buffer, size_t buflen,
  */
 CURL_EXTERN CURLcode curl_ws_send(CURL *curl, const void *buffer,
                                   size_t buflen, size_t *sent,
+                                  curl_off_t framesize,
                                   unsigned int sendflags);
 
 /* bits for the CURLOPT_WS_OPTIONS bitmask: */
 #define CURLWS_RAW_MODE (1<<0)
 
-struct curl_ws_metadata {
+CURL_EXTERN struct curl_ws_frame *curl_ws_meta(CURL *curl);
-  int age;       /* zero */
-  int recvflags; /* See the CURLWS_* defines */
-};
-
-CURL_EXTERN struct curl_ws_metadata *curl_ws_meta(CURL *curl);
 
 #ifdef  __cplusplus
 }

lib/easy.c

@@ -1235,7 +1235,7 @@ CURLcode curl_easy_recv(struct Curl_easy *data, void *buffer, size_t buflen,
  * This is the private internal version of curl_easy_send()
  */
 CURLcode Curl_senddata(struct Curl_easy *data, const void *buffer,
-                       size_t buflen, size_t *n)
+                       size_t buflen, ssize_t *n)
 {
   curl_socket_t sfd;
   CURLcode result;
@@ -1279,7 +1279,7 @@ CURLcode curl_easy_send(struct Curl_easy *data, const void *buffer,
   if(Curl_is_in_callback(data))
     return CURLE_RECURSIVE_API_CALL;
 
-  return Curl_senddata(data, buffer, buflen, n);
+  return Curl_senddata(data, buffer, buflen, (ssize_t *)n);
 }
 
 /*

lib/easyif.h

@@ -28,7 +28,7 @@
  * Prototypes for library-wide functions provided by easy.c
  */
 CURLcode Curl_senddata(struct Curl_easy *data, const void *buffer,
-                       size_t buflen, size_t *n);
+                       size_t buflen, ssize_t *n);
 
 #ifdef CURLDEBUG
 CURL_EXTERN CURLcode curl_easy_perform_ev(struct Curl_easy *easy);

lib/http.h

@@ -202,17 +202,6 @@ struct h3out; /* see ngtcp2 */
 #endif /* _WIN32 */
 #endif /* USE_MSH3 */
 
-struct websockets {
-  bool contfragment; /* set TRUE if the previous fragment sent was not final */
-  unsigned char mask[4]; /* 32 bit mask for this connection */
-  struct Curl_easy *data; /* used for write callback handling */
-  struct dynbuf buf;
-  size_t usedbuf; /* number of leading bytes in 'buf' the most recent complete
-                     websocket frame uses */
-  struct curl_ws_metadata handout; /* the struct storage used for
-                                      curl_ws_meta() returns */
-};
-
 /****************************************************************************
  * HTTP unique setup
  ***************************************************************************/
@@ -240,7 +229,7 @@ struct HTTP {
   } sending;
 
 #ifdef USE_WEBSOCKETS
-  struct websockets ws;
+  struct websocket ws;
 #endif
 
 #ifndef CURL_DISABLE_HTTP

lib/ws.c

@@ -120,6 +120,7 @@ CURLcode Curl_ws_accept(struct Curl_easy *data)
   struct SingleRequest *k = &data->req;
   struct HTTP *ws = data->req.p.http;
   struct connectdata *conn = data->conn;
+  struct websocket *wsp = &data->req.p.http->ws;
   CURLcode result;
 
   /* Verify the Sec-WebSocket-Accept response.
@@ -146,7 +147,7 @@ CURLcode Curl_ws_accept(struct Curl_easy *data)
   if(result)
     return result;
 
-  infof(data, "Received 101, switch to WebSockets; mask %02x%02x%02x%02x",
+  infof(data, "Received 101, switch to WebSocket; mask %02x%02x%02x%02x",
         ws->ws.mask[0], ws->ws.mask[1], ws->ws.mask[2], ws->ws.mask[3]);
   k->upgr101 = UPGR101_RECEIVED;
 
@@ -154,6 +155,7 @@ CURLcode Curl_ws_accept(struct Curl_easy *data)
     /* switch off non-blocking sockets */
     (void)curlx_nonblock(conn->sock[FIRSTSOCKET], FALSE);
 
+  wsp->oleft = 0;
   return result;
 }
 
@@ -172,7 +174,7 @@ CURLcode Curl_ws_accept(struct Curl_easy *data)
    now been delivered to the application */
 static void ws_decode_clear(struct Curl_easy *data)
 {
-  struct websockets *wsp = &data->req.p.http->ws;
+  struct websocket *wsp = &data->req.p.http->ws;
   size_t spent = wsp->usedbuf;
   size_t len = Curl_dyn_len(&wsp->buf);
   size_t keep = len - spent;
@@ -186,6 +188,7 @@ static void ws_decode_clear(struct Curl_easy *data)
    ilen - the size of the provided data, perhaps too little, perhaps too much
    out - stored pointed to extracted data
    olen - stored length of the extracted data
+   oleft - number of unread bytes pending to that belongs to this frame
    endp - stored pointer to data immediately following the parsed data, if
           there is more data in there. NULL if there's no more data.
    flags - stored bitmask about the frame
@@ -198,16 +201,17 @@ static void ws_decode_clear(struct Curl_easy *data)
 static CURLcode ws_decode(struct Curl_easy *data,
                           unsigned char *wpkt, size_t ilen,
                           unsigned char **out, size_t *olen,
+                          curl_off_t *oleft,
                           unsigned char **endp,
                           unsigned int *flags)
 {
   bool fin;
   unsigned char opcode;
-  size_t total;
+  curl_off_t total;
   size_t dataindex = 2;
-  size_t plen; /* size of data in the buffer */
+  curl_off_t plen; /* size of data in the buffer */
-  size_t payloadssize;
+  curl_off_t payloadsize;
-  struct websockets *wsp = &data->req.p.http->ws;
+  struct websocket *wsp = &data->req.p.http->ws;
   unsigned char *p;
   CURLcode result;
 
@@ -266,36 +270,52 @@ static CURLcode ws_decode(struct Curl_easy *data,
     failf(data, "WS: masked input frame");
     return CURLE_RECV_ERROR;
   }
-  payloadssize = p[1];
+  payloadsize = p[1];
-  if(payloadssize == 126) {
+  if(payloadsize == 126) {
     if(plen < 4) {
       infof(data, "WS:%d plen == %u, EAGAIN", __LINE__, (int)plen);
       return CURLE_AGAIN; /* not enough data available */
     }
-    payloadssize = (p[2] << 8) | p[3];
+    payloadsize = (p[2] << 8) | p[3];
     dataindex += 2;
   }
-  else if(payloadssize == 127) {
+  else if(payloadsize == 127) {
-    failf(data, "WS: too large frame received");
+    /* 64 bit payload size */
-    return CURLE_RECV_ERROR;
+    if(plen < 10)
+      return CURLE_AGAIN;
+    if(p[2] & 80) {
+      failf(data, "WS: too large frame");
+      return CURLE_RECV_ERROR;
+    }
+    dataindex += 8;
+    payloadsize = ((curl_off_t)p[2] << 56) |
+      (curl_off_t)p[3] << 48 |
+      (curl_off_t)p[4] << 40 |
+      (curl_off_t)p[5] << 32 |
+      (curl_off_t)p[6] << 24 |
+      (curl_off_t)p[7] << 16 |
+      (curl_off_t)p[8] << 8 |
+      p[9];
   }
 
-  total = dataindex + payloadssize;
+  total = dataindex + payloadsize;
   if(total > plen) {
-    /* not enough data in buffer yet */
+    /* deliver a partial frame */
-    infof(data, "WS:%d plen == %u (%u), EAGAIN", __LINE__, (int)plen,
+    *oleft = total - dataindex;
-          (int)total);
+    payloadsize = total - dataindex;
-    return CURLE_AGAIN;
   }
+  else
+    *oleft = 0;
 
   /* point to the payload */
   *out = &p[dataindex];
 
   /* return the payload length */
-  *olen = payloadssize;
+  *olen = payloadsize;
   wsp->usedbuf = total; /* number of bytes "used" from the buffer */
   *endp = &p[total];
-  infof(data, "WS: received %zu bytes payload", payloadssize);
+  infof(data, "WS: received %zu bytes payload (%zu left)",
+        payloadsize, *oleft);
   return CURLE_OK;
 }
 
@@ -312,40 +332,52 @@ size_t Curl_ws_writecb(char *buffer, size_t size /* 1 */,
   if(data->set.ws_raw_mode)
     return data->set.fwrite_func(buffer, size, nitems, writebody_ptr);
   else if(nitems) {
-    unsigned char *wsp;
+    unsigned char *frame;
-    size_t wslen;
+    size_t flen;
     unsigned int recvflags;
     CURLcode result;
     unsigned char *endp;
+    curl_off_t oleft;
+
     decode:
-    result = ws_decode(data, (unsigned char *)buffer, nitems,
+
-                       &wsp, &wslen, &endp, &recvflags);
+    oleft = ws->ws.frame.bytesleft;
-    if(result == CURLE_AGAIN)
+    if(!oleft) {
-      /* insufficient amount of data, keep it for later */
+      result = ws_decode(data, (unsigned char *)buffer, nitems,
-      return nitems;
+                         &frame, &flen, &oleft, &endp, &recvflags);
-    else if(result) {
+      if(result == CURLE_AGAIN)
-      infof(data, "WS: decode error %d", (int)result);
+        /* insufficient amount of data, keep it for later */
-      return nitems - 1;
+        return nitems;
+      else if(result) {
+        infof(data, "WS: decode error %d", (int)result);
+        return nitems - 1;
+      }
+      /* Store details about the frame to be reachable with curl_ws_meta()
+         from within the write callback */
+      ws->ws.frame.age = 0;
+      ws->ws.frame.offset = 0;
+      ws->ws.frame.flags = recvflags;
+      ws->ws.frame.bytesleft = oleft;
+    }
+    else {
+      ws->ws.frame.bytesleft -= nitems;
     }
     /* auto-respond to PINGs */
-    if(recvflags & CURLWS_PING) {
+    if((recvflags & CURLWS_PING) && !oleft) {
       size_t bytes;
       infof(data, "WS: auto-respond to PING with a PONG");
       /* send back the exact same content as a PONG */
-      result = curl_ws_send(data, wsp, wslen, &bytes, CURLWS_PONG);
+      result = curl_ws_send(data, frame, flen, &bytes, 0, CURLWS_PONG);
       if(result)
         return result;
     }
     else {
-      /* Store details about the frame to be reachable with curl_ws_meta()
-         from within the write callback */
-      ws->ws.handout.age = 0;
-      ws->ws.handout.recvflags = recvflags;
-
       /* deliver the decoded frame to the user callback */
-      if(data->set.fwrite_func((char *)wsp, 1, wslen, writebody_ptr) != wslen)
+      if(data->set.fwrite_func((char *)frame, 1, flen, writebody_ptr) != flen)
         return 0;
     }
+    if(oleft)
+      ws->ws.frame.offset += flen;
     /* the websocket frame has been delivered */
     ws_decode_clear(data);
     if(endp) {
@@ -359,43 +391,70 @@ size_t Curl_ws_writecb(char *buffer, size_t size /* 1 */,
 
 
 CURL_EXTERN CURLcode curl_ws_recv(struct Curl_easy *data, void *buffer,
-                                  size_t buflen,
+                                  size_t buflen, size_t *nread,
-                                  size_t *nread, unsigned int *recvflags)
+                                  struct curl_ws_frame **metap)
 {
   size_t bytes;
   CURLcode result;
+  struct websocket *wsp = &data->req.p.http->ws;
 
   *nread = 0;
-  *recvflags = 0;
+  *metap = NULL;
   /* get a download buffer */
   result = Curl_preconnect(data);
   if(result)
     return result;
 
   do {
-    result = curl_easy_recv(data, data->state.buffer,
+    bool drain = FALSE; /* if there is pending buffered data to drain */
-                            data->set.buffer_size, &bytes);
+    char *inbuf = data->state.buffer;
-    if(result)
+    bytes = wsp->stillbuffer;
-      return result;
+    if(!bytes) {
-
+      result = curl_easy_recv(data, data->state.buffer,
+                              data->set.buffer_size, &bytes);
+      if(result)
+        return result;
+    }
+    else {
+      /* the pending bytes can be found here */
+      inbuf = wsp->stillb;
+      drain = TRUE;
+    }
     if(bytes) {
       unsigned char *out;
       size_t olen;
       unsigned char *endp;
+      unsigned int recvflags;
+      curl_off_t oleft = wsp->frame.bytesleft;
+
       infof(data, "WS: got %u websocket bytes to decode", (int)bytes);
-      result = ws_decode(data, (unsigned char *)data->state.buffer,
+      if(!oleft && !drain) {
-                         bytes, &out, &olen, &endp, recvflags);
+        result = ws_decode(data, (unsigned char *)inbuf, bytes,
-      if(result == CURLE_AGAIN)
+                           &out, &olen, &oleft, &endp, &recvflags);
-        /* a packet fragment only */
+        if(result == CURLE_AGAIN)
-        break;
+          /* a packet fragment only */
-      else if(result)
+          break;
-        return result;
+        else if(result)
+          return result;
+        wsp->frame.offset = 0;
+        wsp->frame.bytesleft = oleft;
+        wsp->frame.flags = recvflags;
+      }
+      else {
+        olen = oleft;
+        recvflags = wsp->frame.flags;
+        if((curl_off_t)buflen < oleft)
+          /* there is still data left after this */
+          wsp->frame.bytesleft -= buflen;
+        else
+          wsp->frame.bytesleft = 0;
+      }
 
       /* auto-respond to PINGs */
-      if(*recvflags & CURLWS_PING) {
+      if((recvflags & CURLWS_PING) && !oleft) {
         infof(data, "WS: auto-respond to PING with a PONG");
         /* send back the exact same content as a PONG */
-        result = curl_ws_send(data, out, olen, &bytes, CURLWS_PONG);
+        result = curl_ws_send(data, out, olen, &bytes, 0, CURLWS_PONG);
         if(result)
           return result;
       }
@@ -404,24 +463,44 @@ CURL_EXTERN CURLcode curl_ws_recv(struct Curl_easy *data, void *buffer,
           /* copy the payload to the user buffer */
           memcpy(buffer, out, olen);
           *nread = olen;
+          if(!oleft)
+            /*  websocket frame has been delivered */
+            ws_decode_clear(data);
         }
         else {
-          /* Received a larger websocket frame than what could fit in the user
+          /* copy a partial payload */
-             provided buffer! */
+          memcpy(buffer, out, buflen);
-          infof(data, "WS: too large websocket frame received");
+          *nread = buflen;
-          return CURLE_RECV_ERROR;
+          /* remember what is left and where */
+          wsp->stillbuffer = olen - buflen;
+          wsp->stillb = (char *)buffer + buflen;
         }
+        wsp->frame.offset += *nread;
       }
-      /* the websocket frame has been delivered */
-      ws_decode_clear(data);
     }
     else
       *nread = bytes;
     break;
   } while(1);
+  *metap = &wsp->frame;
   return CURLE_OK;
 }
 
+static void ws_xor(struct Curl_easy *data,
+                   const unsigned char *source,
+                   unsigned char *dest,
+                   size_t len)
+{
+  struct websocket *wsp = &data->req.p.http->ws;
+  size_t i;
+  /* append payload after the mask, XOR appropriately */
+  for(i = 0; i < len; i++) {
+    dest[i] = source[i] ^ wsp->mask[wsp->xori];
+    wsp->xori++;
+    wsp->xori &= 3;
+  }
+}
+
 /***
     RFC 6455 Section 5.2
 
@@ -445,17 +524,14 @@ CURL_EXTERN CURLcode curl_ws_recv(struct Curl_easy *data, void *buffer,
      +---------------------------------------------------------------+
 */
 
-static size_t ws_packet(struct Curl_easy *data,
+static size_t ws_packethead(struct Curl_easy *data,
-                        const unsigned char *payload, size_t len,
+                            size_t len, unsigned int flags)
-                        unsigned int flags)
 {
   struct HTTP *ws = data->req.p.http;
   unsigned char *out = (unsigned char *)data->state.ulbuf;
   unsigned char firstbyte = 0;
   int outi;
   unsigned char opcode;
-  unsigned int xori;
-  unsigned int i;
   if(flags & CURLWS_TEXT) {
     opcode = WSBIT_OPCODE_TEXT;
     infof(data, "WS: send OPCODE TEXT");
@@ -491,8 +567,13 @@ static size_t ws_packet(struct Curl_easy *data,
     ws->ws.contfragment = TRUE;
   }
   out[0] = firstbyte;
+  if(len > 65535) {
+    out[1] = 127 | WSBIT_MASK;
+    out[2] = (len >> 8) & 0xff;
+    out[3] = len & 0xff;
+    outi = 10;
+  }
   if(len > 126) {
-    /* no support for > 16 bit fragment sizes */
     out[1] = 126 | WSBIT_MASK;
     out[2] = (len >> 8) & 0xff;
     out[3] = len & 0xff;
@@ -517,112 +598,138 @@ static size_t ws_packet(struct Curl_easy *data,
   /* pass over the mask */
   outi += 4;
 
-  /* append payload after the mask, XOR appropriately */
+  ws->ws.xori = 0;
-  for(i = 0, xori = 0; i < len; i++, outi++) {
-    out[outi] = payload[i] ^ ws->ws.mask[xori];
-    xori++;
-    xori &= 3;
-  }
-
   /* return packet size */
   return outi;
 }
 
 CURL_EXTERN CURLcode curl_ws_send(struct Curl_easy *data, const void *buffer,
                                   size_t buflen, size_t *sent,
+                                  curl_off_t totalsize,
                                   unsigned int sendflags)
 {
-  size_t bytes;
   CURLcode result;
-  size_t plen;
+  size_t headlen;
   char *out;
-
+  ssize_t written;
-  if(buflen > MAX_WS_SIZE) {
+  struct websocket *wsp = &data->req.p.http->ws;
-    failf(data, "too large packet");
-    return CURLE_BAD_FUNCTION_ARGUMENT;
-  }
 
   if(!data->set.ws_raw_mode) {
     result = Curl_get_upload_buffer(data);
     if(result)
       return result;
   }
+  else {
+    if(totalsize || sendflags)
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+  }
 
-  if(Curl_is_in_callback(data)) {
+  if(data->set.ws_raw_mode) {
-    ssize_t written;
+    if(!buflen)
-    if(data->set.ws_raw_mode) {
+      /* nothing to do */
-      /* raw mode sends exactly what was requested, and this is from within
+      return CURLE_OK;
-         the write callback */
+    /* raw mode sends exactly what was requested, and this is from within
+       the write callback */
+    if(Curl_is_in_callback(data))
       result = Curl_write(data, data->conn->writesockfd, buffer, buflen,
                           &written);
-      infof(data, "WS: wanted to send %u bytes, sent %u bytes",
+    else
-            (int)buflen, (int)written);
+      result = Curl_senddata(data, buffer, buflen, &written);
+
+    infof(data, "WS: wanted to send %zu bytes, sent %zu bytes",
+          buflen, written);
+    *sent = written;
+    return result;
+  }
+
+  if(buflen > (data->set.upload_buffer_size - 10))
+    /* don't do more than this in one go */
+    buflen = data->set.upload_buffer_size - 10;
+
+  if(sendflags & CURLWS_OFFSET) {
+    if(totalsize) {
+      /* a frame series 'totalsize' bytes big, this is the first */
+      headlen = ws_packethead(data, totalsize, sendflags);
+      wsp->sleft = totalsize - buflen;
     }
     else {
-      plen = ws_packet(data, buffer, buflen, sendflags);
+      headlen = 0;
-      out = data->state.ulbuf;
+      if((curl_off_t)buflen > wsp->sleft) {
-      result = Curl_write(data, data->conn->writesockfd, out, plen,
+        infof(data, "WS: unaligned frame size (sending %zu instead of %zu)",
-                          &written);
+              buflen, wsp->sleft);
-      infof(data, "WS: wanted to send %u bytes, sent %u bytes",
+        wsp->sleft = 0;
-            (int)plen, (int)written);
+      }
+      else
+        wsp->sleft -= buflen;
     }
-    bytes = written;
   }
-  else {
+  else
-    plen = ws_packet(data, buffer, buflen, sendflags);
+    headlen = ws_packethead(data, buflen, sendflags);
 
-    out = data->state.ulbuf;
+  /* headlen is the size of the frame header */
-    result = Curl_senddata(data, out, plen, &bytes);
+  out = data->state.ulbuf;
-    (void)sendflags;
+  if(buflen)
-  }
+    /* for PING and PONG etc there might not be a payload */
-  *sent = bytes;
+    ws_xor(data, buffer, (unsigned char *)out + headlen, buflen - headlen);
+  if(Curl_is_in_callback(data))
+    result = Curl_write(data, data->conn->writesockfd, out,
+                        buflen + headlen, &written);
+  else
+    result = Curl_senddata(data, out, buflen + headlen, &written);
+
+  infof(data, "WS: wanted to send %zu bytes, sent %zu bytes",
+        headlen + buflen, written);
+  *sent = written;
 
   return result;
 }
 
 void Curl_ws_done(struct Curl_easy *data)
 {
-  struct websockets *wsp = &data->req.p.http->ws;
+  struct websocket *wsp = &data->req.p.http->ws;
   DEBUGASSERT(wsp);
   Curl_dyn_free(&wsp->buf);
 }
 
-CURL_EXTERN struct curl_ws_metadata *curl_ws_meta(struct Curl_easy *data)
+CURL_EXTERN struct curl_ws_frame *curl_ws_meta(struct Curl_easy *data)
 {
-  /* we only return something for websockets, called from within the callback
+  /* we only return something for websocket, called from within the callback
      when not using raw mode */
   if(GOOD_EASY_HANDLE(data) && Curl_is_in_callback(data) && data->req.p.http &&
      !data->set.ws_raw_mode)
-    return &data->req.p.http->ws.handout;
+    return &data->req.p.http->ws.frame;
   return NULL;
 }
 
 #else
 
 CURL_EXTERN CURLcode curl_ws_recv(CURL *curl, void *buffer, size_t buflen,
-                                  size_t *nread, unsigned int *recvflags)
+                                  size_t *nread,
+                                  struct curl_ws_frame **metap)
 {
   (void)curl;
   (void)buffer;
   (void)buflen;
   (void)nread;
-  (void)recvflags;
+  (void)metap;
   return CURLE_OK;
 }
 
 CURL_EXTERN CURLcode curl_ws_send(CURL *curl, const void *buffer,
                                   size_t buflen, size_t *sent,
+                                  curl_off_t framesize,
                                   unsigned int sendflags)
 {
   (void)curl;
   (void)buffer;
   (void)buflen;
   (void)sent;
+  (void)framesize;
   (void)sendflags;
   return CURLE_OK;
 }
 
-CURL_EXTERN struct curl_ws_metadata *curl_ws_meta(struct Curl_easy *data)
+CURL_EXTERN struct curl_ws_frame *curl_ws_meta(struct Curl_easy *data)
 {
   (void)data;
   return NULL;

lib/ws.h

@@ -36,6 +36,25 @@
 /* this is the largest single fragment size we support */
 #define MAX_WS_SIZE 65535
 
+/* part of 'struct HTTP', when used in the 'struct SingleRequest' in the
+   Curl_easy struct */
+struct websocket {
+  bool contfragment; /* set TRUE if the previous fragment sent was not final */
+  unsigned char mask[4]; /* 32 bit mask for this connection */
+  struct Curl_easy *data; /* used for write callback handling */
+  struct dynbuf buf;
+  size_t usedbuf; /* number of leading bytes in 'buf' the most recent complete
+                     websocket frame uses */
+  struct curl_ws_frame frame; /* the struct used for frame state */
+  curl_off_t oleft; /* outstanding number of payload bytes left from the
+                       server */
+  curl_off_t stillbuffer; /* number of bytes left in the buffer to deliver in
+                             the next curl_ws_recv() call */
+  char *stillb; /* the stillbuffer pending bytes are here */
+  curl_off_t sleft; /* outstanding number of payload bytes left to send */
+  unsigned int xori; /* xor index */
+};
+
 CURLcode Curl_ws_request(struct Curl_easy *data, REQTYPE *req);
 CURLcode Curl_ws_accept(struct Curl_easy *data);
 

tests/libtest/lib2301.c

@@ -110,7 +110,7 @@ static size_t writecb(char *b, size_t size, size_t nitems, void *p)
   if(buffer[0] == 0x89) {
     CURLcode result;
     fprintf(stderr, "send back a simple PONG\n");
-    result = curl_ws_send(easy, pong, 2, &sent, 0);
+    result = curl_ws_send(easy, pong, 2, &sent, 0, 0);
     if(result)
       nitems = 0;
   }

tests/libtest/lib2302.c

@@ -97,7 +97,7 @@ static size_t writecb(char *buffer, size_t size, size_t nitems, void *p)
   CURL *easy = p;
   size_t i;
   size_t incoming = nitems;
-  struct curl_ws_metadata *meta;
+  struct curl_ws_frame *meta;
   (void)size;
   for(i = 0; i < nitems; i++)
     printf("%02x ", (unsigned char)buffer[i]);
@@ -105,7 +105,7 @@ static size_t writecb(char *buffer, size_t size, size_t nitems, void *p)
 
   meta = curl_ws_meta(easy);
   if(meta)
-    printf("RECFLAGS: %x\n", meta->recvflags);
+    printf("RECFLAGS: %x\n", meta->flags);
   else
     fprintf(stderr, "RECFLAGS: NULL\n");