http: Implement trailing headers for chunked transfers

This adds the CURLOPT_TRAILERDATA and CURLOPT_TRAILERFUNCTION
options that allow a callback based approach to sending trailing headers
with chunked transfers.

The test server (sws) was updated to take into account the detection of the
end of transfer in the case of trailing headers presence.

Test 1591 checks that trailing headers can be sent using libcurl.

Closes #3350

17 files changed, 618 insertions, 22 deletions

diff --git a/docs/libcurl/curl_easy_setopt.3 b/docs/libcurl/curl_easy_setopt.3
index f4b89c2f8..1bec4c14d 100644
--- a/docs/libcurl/curl_easy_setopt.3
+++ b/docs/libcurl/curl_easy_setopt.3
@@ -327,6 +327,12 @@ Disable Content decoding. See \fICURLOPT_HTTP_CONTENT_DECODING(3)\fP
 Disable Transfer decoding. See \fICURLOPT_HTTP_TRANSFER_DECODING(3)\fP
 .IP CURLOPT_EXPECT_100_TIMEOUT_MS
 100-continue timeout. See \fICURLOPT_EXPECT_100_TIMEOUT_MS(3)\fP
+.IP CURLOPT_TRAILERFUNCTION
+Set callback for sending trailing headers. See
+\fICURLOPT_TRAILERFUNCTION(3)\fP
+.IP CURLOPT_TRAILERDATA
+Custom pointer passed to the trailing headers callback. See
+\fICURLOPT_TRAILERDATA(3)\fP
 .IP CURLOPT_PIPEWAIT
 Wait on connection to pipeline on it. See \fICURLOPT_PIPEWAIT(3)\fP
 .IP CURLOPT_STREAM_DEPENDS
diff --git a/docs/libcurl/opts/CURLOPT_TRAILERDATA.3 b/docs/libcurl/opts/CURLOPT_TRAILERDATA.3
new file mode 100644
index 000000000..32fadd4ac
--- /dev/null
+++ b/docs/libcurl/opts/CURLOPT_TRAILERDATA.3
@@ -0,0 +1,57 @@
+.\" **************************************************************************
+.\" *                                  _   _ ____  _
+.\" *  Project                     ___| | | |  _ \| |
+.\" *                             / __| | | | |_) | |
+.\" *                            | (__| |_| |  _ <| |___
+.\" *                             \___|\___/|_| \_\_____|
+.\" *
+.\" * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" *
+.\" * This software is licensed as described in the file COPYING, which
+.\" * you should have received as part of this distribution. The terms
+.\" * are also available at https://curl.haxx.se/docs/copyright.html.
+.\" *
+.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+.\" * copies of the Software, and permit persons to whom the Software is
+.\" * furnished to do so, under the terms of the COPYING file.
+.\" *
+.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+.\" * KIND, either express or implied.
+.\" *
+.\" **************************************************************************
+.\"
+.TH CURLOPT_TRAILERDATA 3 "14 Aug 2018" "libcurl 7.64.0" "curl_easy_setopt options"
+
+.SH NAME:
+CURLOPT_TRAILERDATA \- Custom pointer passed to the trailing headers callback
+		
+.SH SYNOPSIS:
+#include <curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TRAILERDATA, void *userdata);
+
+.SH DESCRIPTION:
+Data pointer to be passed to the HTTP trailer callback function.
+
+.SH DEFAULT:
+NULL
+
+.SH PROTOCOLS:
+HTTP
+
+.SH EXAMPLE:
+.nf
+/* Assuming we have a CURL handle in the hndl variable. */
+
+struct MyData data;
+
+curl_easy_setopt(hndl, CURLOPT_TRAILERDATA, &data);
+
+.fi
+
+A more complete example can be found in examples/http_trailers.html
+.SH AVAILABILITY:
+This option was added in curl 7.64.0 and is present if HTTP support is enabled
+
+.SH "SEE ALSO"
+.BR CURLOPT_TRAILERFUNCTION "(3), "
diff --git a/docs/libcurl/opts/CURLOPT_TRAILERFUNCTION.3 b/docs/libcurl/opts/CURLOPT_TRAILERFUNCTION.3
new file mode 100644
index 000000000..8ca132362
--- /dev/null
+++ b/docs/libcurl/opts/CURLOPT_TRAILERFUNCTION.3
@@ -0,0 +1,112 @@
+.\" **************************************************************************
+.\" *                                  _   _ ____  _
+.\" *  Project                     ___| | | |  _ \| |
+.\" *                             / __| | | | |_) | |
+.\" *                            | (__| |_| |  _ <| |___
+.\" *                             \___|\___/|_| \_\_____|
+.\" *
+.\" * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" *
+.\" * This software is licensed as described in the file COPYING, which
+.\" * you should have received as part of this distribution. The terms
+.\" * are also available at https://curl.haxx.se/docs/copyright.html.
+.\" *
+.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+.\" * copies of the Software, and permit persons to whom the Software is
+.\" * furnished to do so, under the terms of the COPYING file.
+.\" *
+.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+.\" * KIND, either express or implied.
+.\" *
+.\" **************************************************************************
+.\"
+.TH CURLOPT_TRAILERFUNCTION 3 "14 Aug 2018" "libcurl 7.64.0" "curl_easy_setopt options"
+
+.SH NAME:
+CURLOPT_TRAILERFUNCTION \- Set callback for sending trailing headers
+
+.SH SYNOPSIS:
+#include <curl.h>
+
+int curl_trailer_callback(struct curl_slist ** list, void *userdata);
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TRAILERFUNCTION, curl_trailer_callback *func);
+
+.SH DESCRIPTION:
+Pass a pointer to a callback function.
+
+This callback function will be called once right before sending the final
+CR LF in an HTTP chunked transfer to fill a list of trailing headers to be
+sent before finishing the HTTP transfer.
+
+You can set the userdata argument with the CURLOPT_TRAILERDATA option.
+
+The trailing headers included in the linked list must not be CRLF-terminated,
+because libcurl will add the appropriate line termination characters after
+each header item.
+
+If you use curl_slist_append to add trailing headers to the curl_slist then
+libcurl will duplicate the strings, and will free the curl_slist and the
+duplicates once the trailers have been sent.
+
+If one of the trailing headers is not formatted correctly
+(i.e. HeaderName: headerdata) it will be ignored and an info message
+will be emitted.
+
+The return value can either be CURL_TRAILERFUNC_OK or CURL_TRAILERFUNC_ABORT
+which would respectively instruct libcurl to either continue with sending the
+trailers or to abort the request.
+
+If you set this option to NULL, then the transfer proceeds as usual
+without any interruptions.
+
+.SH DEFAULT:
+NULL
+
+.SH PROTOCOLS:
+HTTP
+
+.SH EXAMPLE:
+#include <curl/curl.h>
+
+static int trailer_cb(struct curl_slist **tr, void *data)
+{
+    /* libcurl will free the list */
+	*tr = curl_slist_append(*tr, "My-super-awesome-trailer: trailer-stuff");
+	(void)data;
+	return CURL_TRAILERFUNC_OK;
+}
+
+CURL *curl = curl_easy_init();
+if(curl) {
+
+    /* Set the URL of the request */
+    curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/");
+    /* Now set it as a put */
+    curl_easy_setopt(curl, CURLOPT_PUT, 1L);
+    
+    /* Assuming we have a function that will return the data to be pushed 
+       Let that function be read_cb */
+    curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_cb);
+
+    struct curl_slist *headers = NULL;
+    headers = curl_slist_append(headers, "Trailer: My-super-awsome-trailer");
+    res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
+
+    /* Set the trailers filling callback */
+    curl_easy_setopt(curl, CURLOPT_TRAILERFUNCTION, (curl_trailer_callback)trailer_cb);
+
+    /* Perform the request, res will get the return code */ 
+    res = curl_easy_perform(curl);
+
+    curl_easy_cleanup(curl);
+
+    curl_slist_free_all(headers);
+}
+
+
+.SH AVAILABILITY:
+This option was added in curl 7.64.0 and is present if HTTP support is enabled
+
+.SH "SEE ALSO"
+.BR CURLOPT_TRAILERDATA "(3), "
diff --git a/docs/libcurl/opts/Makefile.inc b/docs/libcurl/opts/Makefile.inc
index e58db5f4a..9bfd555f1 100644
--- a/docs/libcurl/opts/Makefile.inc
+++ b/docs/libcurl/opts/Makefile.inc
@@ -163,6 +163,8 @@ man_MANS =                                      \
   CURLOPT_HTTP_CONTENT_DECODING.3               \
   CURLOPT_HTTP_TRANSFER_DECODING.3              \
   CURLOPT_HTTP_VERSION.3                        \
+  CURLOPT_TRAILERFUNCTION.3                     \
+  CURLOPT_TRAILERDATA.3                         \
   CURLOPT_IGNORE_CONTENT_LENGTH.3               \
   CURLOPT_INFILESIZE.3                          \
   CURLOPT_INFILESIZE_LARGE.3                    \
diff --git a/docs/libcurl/symbols-in-versions b/docs/libcurl/symbols-in-versions
index 6c17c384c..8659346ce 100644
--- a/docs/libcurl/symbols-in-versions
+++ b/docs/libcurl/symbols-in-versions
@@ -431,6 +431,8 @@ CURLOPT_HTTPREQUEST             7.1           -           7.15.5
 CURLOPT_HTTP_CONTENT_DECODING   7.16.2
 CURLOPT_HTTP_TRANSFER_DECODING  7.16.2
 CURLOPT_HTTP_VERSION            7.9.1
+CURLOPT_TRAILERFUNCTION         7.64.0
+CURLOPT_TRAILERDATA             7.64.0
 CURLOPT_IGNORE_CONTENT_LENGTH   7.14.1
 CURLOPT_INFILE                  7.1           7.9.7
 CURLOPT_INFILESIZE              7.1
@@ -851,6 +853,8 @@ CURL_PUSH_DENY                  7.44.0
 CURL_PUSH_OK                    7.44.0
 CURL_READFUNC_ABORT             7.12.1
 CURL_READFUNC_PAUSE             7.18.0
+CURL_TRAILERFUNC_OK             7.64.0
+CURL_TRAILERFUNC_ABORT          7.64.0
 CURL_REDIR_GET_ALL              7.19.1
 CURL_REDIR_POST_301             7.19.1
 CURL_REDIR_POST_302             7.19.1
diff --git a/include/curl/curl.h b/include/curl/curl.h
index 3c5ce709a..bd6183838 100644
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -355,11 +355,21 @@ typedef int (*curl_seek_callback)(void *instream,
    signal libcurl to pause sending data on the current transfer. */
 #define CURL_READFUNC_PAUSE 0x10000001
 
+/* Return code for when the trailing headers' callback has terminated
+   without any errors*/
+#define CURL_TRAILERFUNC_OK 0
+/* Return code for when was an error in the trailing header's list and we
+  want to abort the request */
+#define CURL_TRAILERFUNC_ABORT 1
+
 typedef size_t (*curl_read_callback)(char *buffer,
                                       size_t size,
                                       size_t nitems,
                                       void *instream);
 
+typedef int (*curl_trailer_callback)(struct curl_slist **list,
+                                      void *userdata);
+
 typedef enum {
   CURLSOCKTYPE_IPCXN,  /* socket created for a specific IP connection */
   CURLSOCKTYPE_ACCEPT, /* socket created by accept() call */
@@ -1875,6 +1885,12 @@ typedef enum {
   /* Specify URL using CURL URL API. */
   CINIT(CURLU, OBJECTPOINT, 282),
 
+  /* add trailing data just after no more data is available */
+  CINIT(TRAILERFUNCTION, FUNCTIONPOINT, 283),
+
+  /* pointer to be passed to HTTP_TRAILER_FUNCTION */
+  CINIT(TRAILERDATA, OBJECTPOINT, 284),
+
   CURLOPT_LASTENTRY /* the last unused */
 } CURLoption;
 
diff --git a/lib/http.c b/lib/http.c
index 0a3e46243..07665743c 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -1681,6 +1681,52 @@ enum proxy_use {
   HEADER_CONNECT  /* sending CONNECT to a proxy */
 };
 
+/* used to compile the provided trailers into one buffer
+   will return an error code if one of the headers is
+   not formatted correctly */
+CURLcode Curl_http_compile_trailers(struct curl_slist *trailers,
+                                    Curl_send_buffer *buffer,
+                                    struct Curl_easy *handle)
+{
+  char *ptr = NULL;
+  CURLcode result = CURLE_OK;
+  const char *endofline_native = NULL;
+  const char *endofline_network = NULL;
+
+  /* TODO: Maybe split Curl_add_custom_headers to make it reusable here */
+
+  if(
+#ifdef CURL_DO_LINEEND_CONV
+     (handle->set.prefer_ascii) ||
+#endif
+     (handle->set.crlf)) {
+    /* \n will become \r\n later on */
+    endofline_native  = "\n";
+    endofline_network = "\x0a";
+  }
+  else {
+    endofline_native  = "\r\n";
+    endofline_network = "\x0d\x0a";
+  }
+
+  while(trailers) {
+    /* only add correctly formatted trailers */
+    ptr = strchr(trailers->data, ':');
+    if(ptr && *(ptr + 1) == ' ') {
+      result = Curl_add_bufferf(&buffer, "%s%s", trailers->data,
+                                endofline_native);
+      if(result)
+        return result;
+    }
+    else
+      infof(handle, "Malformatted trailing header ! Skipping trailer.");
+    trailers = trailers->next;
+  }
+  result = Curl_add_buffer(&buffer, endofline_network,
+                           strlen(endofline_network));
+  return result;
+}
+
 CURLcode Curl_add_custom_headers(struct connectdata *conn,
                                  bool is_connect,
                                  Curl_send_buffer *req_buffer)
diff --git a/lib/http.h b/lib/http.h
index 21fa701ab..7fa0471ad 100644
--- a/lib/http.h
+++ b/lib/http.h
@@ -74,6 +74,9 @@ CURLcode Curl_add_timecondition(struct Curl_easy *data,
 CURLcode Curl_add_custom_headers(struct connectdata *conn,
                                  bool is_connect,
                                  Curl_send_buffer *req_buffer);
+CURLcode Curl_http_compile_trailers(struct curl_slist *trailers,
+                                    Curl_send_buffer *buffer,
+                                    struct Curl_easy *handle);
 
 /* protocol-specific functions set up to be called by the main engine */
 CURLcode Curl_http(struct connectdata *conn, bool *done);
diff --git a/lib/setopt.c b/lib/setopt.c
index 01a890b39..27046768c 100644
--- a/lib/setopt.c
+++ b/lib/setopt.c
@@ -2636,6 +2636,16 @@ CURLcode Curl_vsetopt(struct Curl_easy *data, CURLoption option,
       return CURLE_BAD_FUNCTION_ARGUMENT;
     data->set.upkeep_interval_ms = arg;
     break;
+  case CURLOPT_TRAILERFUNCTION:
+#ifndef CURL_DISABLE_HTTP
+    data->set.trailer_callback = va_arg(param, curl_trailer_callback);
+#endif
+    break;
+  case CURLOPT_TRAILERDATA:
+#ifndef CURL_DISABLE_HTTP
+    data->set.trailer_data = va_arg(param, void *);
+#endif
+    break;
   default:
     /* unknown tag and its companion, just ignore: */
     result = CURLE_UNKNOWN_OPTION;
diff --git a/lib/transfer.c b/lib/transfer.c
index 6390821bb..7483cf1f8 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -117,6 +117,35 @@ CURLcode Curl_get_upload_buffer(struct Curl_easy *data)
   return CURLE_OK;
 }
 
+#ifndef CURL_DISABLE_HTTP
+/*
+ * This function will be called to loop through the trailers buffer
+ * until no more data is available for sending.
+ */
+static size_t Curl_trailers_read(char *buffer, size_t size, size_t nitems,
+                                 void *raw)
+{
+  struct Curl_easy *data = (struct Curl_easy *)raw;
+  Curl_send_buffer *trailers_buf = data->state.trailers_buf;
+  size_t bytes_left = trailers_buf->size_used-data->state.trailers_bytes_sent;
+  size_t to_copy = (size*nitems < bytes_left) ? size*nitems : bytes_left;
+  if(to_copy) {
+    memcpy(buffer,
+           &trailers_buf->buffer[data->state.trailers_bytes_sent],
+           to_copy);
+    data->state.trailers_bytes_sent += to_copy;
+  }
+  return to_copy;
+}
+
+static size_t Curl_trailers_left(void *raw)
+{
+  struct Curl_easy *data = (struct Curl_easy *)raw;
+  Curl_send_buffer *trailers_buf = data->state.trailers_buf;
+  return trailers_buf->size_used - data->state.trailers_bytes_sent;
+}
+#endif
+
 /*
  * This function will call the read callback to fill our buffer with data
  * to upload.
@@ -127,6 +156,17 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, size_t bytes,
   struct Curl_easy *data = conn->data;
   size_t buffersize = bytes;
   size_t nread;
+
+#ifndef CURL_DISABLE_HTTP
+  struct curl_slist *trailers = NULL;
+  CURLcode c;
+  int trailers_ret_code;
+#endif
+
+  curl_read_callback readfunc = NULL;
+  void *extra_data = NULL;
+  bool added_crlf = FALSE;
+
 #ifdef CURL_DOES_CONVERSIONS
   bool sending_http_headers = FALSE;
 
@@ -140,15 +180,71 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, size_t bytes,
   }
 #endif
 
-  if(data->req.upload_chunky) {
+#ifndef CURL_DISABLE_HTTP
+  if(data->state.trailers_state == TRAILERS_INITIALIZED) {
+    /* at this point we already verified that the callback exists
+       so we compile and store the trailers buffer, then proceed */
+    infof(data,
+          "Moving trailers state machine from initialized to sending.\n");
+    data->state.trailers_state = TRAILERS_SENDING;
+    data->state.trailers_buf = Curl_add_buffer_init();
+    if(!data->state.trailers_buf) {
+      failf(data, "Unable to allocate trailing headers buffer !");
+      return CURLE_OUT_OF_MEMORY;
+    }
+    data->state.trailers_bytes_sent = 0;
+    Curl_set_in_callback(data, true);
+    trailers_ret_code = data->set.trailer_callback(&trailers,
+                                                   data->set.trailer_data);
+    Curl_set_in_callback(data, false);
+    if(trailers_ret_code == CURL_TRAILERFUNC_OK) {
+      c = Curl_http_compile_trailers(trailers, data->state.trailers_buf, data);
+    }
+    else {
+      failf(data, "operation aborted by trailing headers callback");
+      *nreadp = 0;
+      c = CURLE_ABORTED_BY_CALLBACK;
+    }
+    if(c != CURLE_OK) {
+      Curl_add_buffer_free(&data->state.trailers_buf);
+      curl_slist_free_all(trailers);
+      return c;
+    }
+    infof(data, "Successfully compiled trailers.\r\n");
+    curl_slist_free_all(trailers);
+  }
+#endif
+
+  /* if we are transmitting trailing data, we don't need to write
+     a chunk size so we skip this */
+  if(data->req.upload_chunky &&
+     data->state.trailers_state == TRAILERS_NONE) {
     /* if chunked Transfer-Encoding */
     buffersize -= (8 + 2 + 2);   /* 32bit hex + CRLF + CRLF */
     data->req.upload_fromhere += (8 + 2); /* 32bit hex + CRLF */
   }
 
+#ifndef CURL_DISABLE_HTTP
+  if(data->state.trailers_state == TRAILERS_SENDING) {
+    /* if we're here then that means that we already sent the last empty chunk
+       but we didn't send a final CR LF, so we sent 0 CR LF. We then start
+       pulling trailing data until we ²have no more at which point we
+       simply return to the previous point in the state machine as if
+       nothing happened.
+       */
+    readfunc = Curl_trailers_read;
+    extra_data = (void *)data;
+  }
+  else
+#endif
+  {
+    readfunc = data->state.fread_func;
+    extra_data = data->state.in;
+  }
+
   Curl_set_in_callback(data, true);
-  nread = data->state.fread_func(data->req.upload_fromhere, 1,
-                                 buffersize, data->state.in);
+  nread = readfunc(data->req.upload_fromhere, 1,
+                   buffersize, extra_data);
   Curl_set_in_callback(data, false);
 
   if(nread == CURL_READFUNC_ABORT) {
@@ -203,7 +299,7 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, size_t bytes,
     char hexbuffer[11];
     const char *endofline_native;
     const char *endofline_network;
-    int hexlen;
+    int hexlen = 0;
 
     if(
 #ifdef CURL_DO_LINEEND_CONV
@@ -218,20 +314,36 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, size_t bytes,
       endofline_native  = "\r\n";
       endofline_network = "\x0d\x0a";
     }
-    hexlen = msnprintf(hexbuffer, sizeof(hexbuffer),
-                       "%x%s", nread, endofline_native);
 
-    /* move buffer pointer */
-    data->req.upload_fromhere -= hexlen;
-    nread += hexlen;
+    /* if we're not handling trailing data, proceed as usual */
+    if(data->state.trailers_state != TRAILERS_SENDING) {
+      hexlen = msnprintf(hexbuffer, sizeof(hexbuffer),
+                         "%x%s", nread, endofline_native);
 
-    /* copy the prefix to the buffer, leaving out the NUL */
-    memcpy(data->req.upload_fromhere, hexbuffer, hexlen);
+      /* move buffer pointer */
+      data->req.upload_fromhere -= hexlen;
+      nread += hexlen;
 
-    /* always append ASCII CRLF to the data */
-    memcpy(data->req.upload_fromhere + nread,
-           endofline_network,
-           strlen(endofline_network));
+      /* copy the prefix to the buffer, leaving out the NUL */
+      memcpy(data->req.upload_fromhere, hexbuffer, hexlen);
+
+      /* always append ASCII CRLF to the data unless
+         we have a valid trailer callback */
+#ifndef CURL_DISABLE_HTTP
+      if((nread-hexlen) == 0 &&
+          data->set.trailer_callback != NULL &&
+          data->state.trailers_state == TRAILERS_NONE) {
+        data->state.trailers_state = TRAILERS_INITIALIZED;
+      }
+      else
+#endif
+      {
+        memcpy(data->req.upload_fromhere + nread,
+               endofline_network,
+               strlen(endofline_network));
+        added_crlf = TRUE;
+      }
+    }
 
 #ifdef CURL_DOES_CONVERSIONS
     {
@@ -251,13 +363,29 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, size_t bytes,
     }
 #endif /* CURL_DOES_CONVERSIONS */
 
-    if((nread - hexlen) == 0) {
-      /* mark this as done once this chunk is transferred */
+#ifndef CURL_DISABLE_HTTP
+    if(data->state.trailers_state == TRAILERS_SENDING &&
+       !Curl_trailers_left(data)) {
+      Curl_add_buffer_free(&data->state.trailers_buf);
+      data->state.trailers_state = TRAILERS_DONE;
+      data->set.trailer_data = NULL;
+      data->set.trailer_callback = NULL;
+      /* mark the transfer as done */
       data->req.upload_done = TRUE;
-      infof(data, "Signaling end of chunked upload via terminating chunk.\n");
+      infof(data, "Signaling end of chunked upload after trailers.\n");
     }
+    else
+#endif
+      if((nread - hexlen) == 0 &&
+         data->state.trailers_state != TRAILERS_INITIALIZED) {
+        /* mark this as done once this chunk is transferred */
+        data->req.upload_done = TRUE;
+        infof(data,
+              "Signaling end of chunked upload via terminating chunk.\n");
+      }
 
-    nread += strlen(endofline_native); /* for the added end of line */
+    if(added_crlf)
+      nread += strlen(endofline_network); /* for the added end of line */
   }
 #ifdef CURL_DOES_CONVERSIONS
   else if((data->set.prefer_ascii) && (!sending_http_headers)) {
@@ -925,7 +1053,6 @@ static CURLcode readwrite_upload(struct Curl_easy *data,
   *didwhat |= KEEP_SEND;
 
   do {
-
     /* only read more data if there's no upload data already
        present in the upload buffer */
     if(0 == k->upload_present) {
@@ -950,7 +1077,6 @@ static CURLcode readwrite_upload(struct Curl_easy *data,
           k->keepon &= ~KEEP_SEND;         /* disable writing */
           k->start100 = Curl_now();       /* timeout count starts now */
           *didwhat &= ~KEEP_SEND;  /* we didn't write anything actually */
-
           /* set a timeout for the multi interface */
           Curl_expire(data, data->set.expect_100_timeout, EXPIRE_100_TIMEOUT);
           break;
diff --git a/lib/urldata.h b/lib/urldata.h
index 448437d2a..8fb2d2894 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -1216,6 +1216,15 @@ typedef enum {
   EXPIRE_LAST /* not an actual timer, used as a marker only */
 } expire_id;
 
+
+typedef enum {
+  TRAILERS_NONE,
+  TRAILERS_INITIALIZED,
+  TRAILERS_SENDING,
+  TRAILERS_DONE
+} trailers_state;
+
+
 /*
  * One instance for each timeout an easy handle can set.
  */
@@ -1362,6 +1371,13 @@ struct UrlState {
 #endif
   CURLU *uh; /* URL handle for the current parsed URL */
   struct urlpieces up;
+#ifndef CURL_DISABLE_HTTP
+  size_t trailers_bytes_sent;
+  Curl_send_buffer *trailers_buf; /* a buffer containing the compiled trailing
+                                  headers */
+#endif
+  trailers_state trailers_state; /* whether we are sending trailers
+                                       and what stage are we at */
 };
 
 
@@ -1730,6 +1746,8 @@ struct UserDefined {
   multidone_func fmultidone;
   struct Curl_easy *dohfor; /* this is a DoH request for that transfer */
   CURLU *uh; /* URL handle for the current parsed URL */
+  void *trailer_data; /* pointer to pass to trailer data callback */
+  curl_trailer_callback trailer_callback; /* trailing data callback */
 };
 
 struct Names {
diff --git a/tests/data/Makefile.inc b/tests/data/Makefile.inc
index 250aa2004..52916c983 100644
--- a/tests/data/Makefile.inc
+++ b/tests/data/Makefile.inc
@@ -179,6 +179,7 @@ test1550 test1551 test1552 test1553 test1554 test1555 test1556 test1557 \
 test1560 test1561 \
 \
 test1590 \
+test1591 \
 test1600 test1601 test1602 test1603 test1604 test1605 test1606 test1607 \
 test1608 test1609 test1620 \
 \
diff --git a/tests/data/test1591 b/tests/data/test1591
new file mode 100644
index 000000000..e864fdbaa
--- /dev/null
+++ b/tests/data/test1591
@@ -0,0 +1,63 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP PUT
+CURLOPT_HTTPTRAILER_FUNCTION
+CURLOPT_HTTPTRAILER_DATA
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data nocheck="yes">
+HTTP/1.0 200 OK swsclose
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake
+</data>
+</reply>
+# Client-side
+<client>
+<features>
+HTTP
+</features>
+<server>
+http
+</server>
+<name>
+HTTP PUT with trailers at the end
+</name>
+<tool>
+lib1591
+</tool>
+<command>
+http://%HOSTIP:%HTTPPORT/bzz/1591
+</command>
+<stdin>
+more than one byte
+</stdin>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<strip>
+^User-Agent:.*
+</strip>
+<protocol>
+PUT /bzz/1591 HTTP/1.1

+Host: %HOSTIP:%HTTPPORT

+Accept: */*

+Transfer-Encoding: chunked

+Trailer: my-super-awesome-trailer, my-other-awesome-trailer

+Expect: 100-continue

+

+e

+Hello Cloud!

+

+0

+my-super-awesome-trailer: trail1

+my-other-awesome-trailer: trail2

+

+</protocol>
+</verify>
+</testcase>
diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index 080421b26..4c41fe7a1 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -31,6 +31,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib1540 \
  lib1550 lib1551 lib1552 lib1553 lib1554 lib1555 lib1556 lib1557 \
  lib1560 \
+ lib1591 \
  lib1900 \
  lib2033
 
@@ -518,6 +519,10 @@ lib1557_CPPFLAGS = $(AM_CPPFLAGS) -DLIB1557
 lib1560_SOURCES = lib1560.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib1560_LDADD = $(TESTUTIL_LIBS)
 
+lib1591_SOURCES = lib1591.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib1591_LDADD = $(TESTUTIL_LIBS)
+lib1591_CPPFLAGS = $(AM_CPPFLAGS) -DLIB1591
+
 lib1900_SOURCES = lib1900.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib1900_LDADD = $(TESTUTIL_LIBS)
 lib1900_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/tests/libtest/lib1591.c b/tests/libtest/lib1591.c
new file mode 100644
index 000000000..7aba22337
--- /dev/null
+++ b/tests/libtest/lib1591.c
@@ -0,0 +1,106 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+/*
+ * This unit test PUT http data over proxy. Proxy header will be different
+ * from server http header
+ */
+
+#include "test.h"
+#include <stdio.h>
+#include "memdebug.h"
+
+static char data [] = "Hello Cloud!\r\n";
+static size_t consumed = 0;
+
+static size_t read_callback(void *ptr, size_t size, size_t nmemb, void *stream)
+{
+  size_t  amount = nmemb * size; /* Total bytes curl wants */
+
+  if(consumed == strlen(data)) {
+    return 0;
+  }
+
+  if(amount > strlen(data)-consumed) {
+    amount = strlen(data);
+  }
+
+  consumed += amount;
+  (void)stream;
+  memcpy(ptr, data, amount);
+  return amount;
+}
+
+static int trailers_callback(struct curl_slist **list, void *userdata)
+{
+  (void)userdata;
+  *list = curl_slist_append(*list, "my-super-awesome-trailer: trail1");
+  *list = curl_slist_append(*list, "my-other-awesome-trailer: trail2");
+  return CURL_TRAILERFUNC_OK;
+}
+
+int test(char *URL)
+{
+  CURL *curl = NULL;
+  CURLcode res = CURLE_FAILED_INIT;
+  /* http and proxy header list*/
+  struct curl_slist *hhl = NULL;
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    fprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+
+  curl = curl_easy_init();
+  if(!curl) {
+    fprintf(stderr, "curl_easy_init() failed\n");
+    curl_global_cleanup();
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  hhl = curl_slist_append(hhl, "Trailer: my-super-awesome-trailer,"
+                               " my-other-awesome-trailer");
+  if(!hhl) {
+    goto test_cleanup;
+  }
+
+  test_setopt(curl, CURLOPT_URL, URL);
+  test_setopt(curl, CURLOPT_HTTPHEADER, hhl);
+  test_setopt(curl, CURLOPT_PUT, 1L);
+  test_setopt(curl, CURLOPT_READFUNCTION, read_callback);
+  test_setopt(curl, CURLOPT_TRAILERFUNCTION, trailers_callback);
+  test_setopt(curl, CURLOPT_TRAILERDATA, NULL);
+
+  res = curl_easy_perform(curl);
+
+test_cleanup:
+
+  curl_easy_cleanup(curl);
+
+  curl_slist_free_all(hhl);
+
+  curl_global_cleanup();
+
+  return (int)res;
+}
+
diff --git a/tests/libtest/mk-lib1521.pl b/tests/libtest/mk-lib1521.pl
index 9771cf57f..fb1401a53 100755
--- a/tests/libtest/mk-lib1521.pl
+++ b/tests/libtest/mk-lib1521.pl
@@ -121,6 +121,7 @@ static int geterr(const char *name, CURLcode val, int lineno)
 static curl_progress_callback progresscb;
 static curl_write_callback headercb;
 static curl_debug_callback debugcb;
+static curl_trailer_callback trailercb;
 static curl_ssl_ctx_callback ssl_ctx_cb;
 static curl_ioctl_callback ioctlcb;
 static curl_sockopt_callback sockoptcb;
diff --git a/tests/server/sws.c b/tests/server/sws.c
index cf3d291d9..87c0204c9 100644
--- a/tests/server/sws.c
+++ b/tests/server/sws.c
@@ -253,6 +253,9 @@ SIG_ATOMIC_T got_exit_signal = 0;
 
 static volatile int exit_signal = 0;
 
+/* work around for handling trailing headers */
+static int already_recv_zeroed_chunk = FALSE;
+
 /* signal handler that will be triggered to indicate that the program
   should finish its execution in a controlled manner as soon as possible.
   The first time this is called it will set got_exit_signal to one and
@@ -755,10 +758,27 @@ static int ProcessRequest(struct httprequest *req)
       chunked = TRUE;
     }
 
+
     if(chunked) {
-      if(strstr(req->reqbuf, "\r\n0\r\n\r\n"))
+      if(strstr(req->reqbuf, "\r\n0\r\n\r\n")) {
         /* end of chunks reached */
         return 1; /* done */
+      }
+      else if(strstr(req->reqbuf, "\r\n0\r\n")) {
+        char *last_crlf_char = strstr(req->reqbuf, "\r\n\r\n");
+        while(TRUE) {
+          if(!strstr(last_crlf_char + 4, "\r\n\r\n"))
+            break;
+          last_crlf_char = strstr(last_crlf_char + 4, "\r\n\r\n");
+        }
+        if(last_crlf_char &&
+           last_crlf_char > strstr(req->reqbuf, "\r\n0\r\n"))
+          return 1;
+        already_recv_zeroed_chunk = TRUE;
+        return 0;
+      }
+      else if(already_recv_zeroed_chunk && strstr(req->reqbuf, "\r\n\r\n"))
+        return 1;
       else
         return 0; /* not done */
     }