new file mode 100644
--- /dev/null
+++ b/src/os/unix/ngx_freebsd_write_chain.c
@@ -0,0 +1,178 @@
+
+#include <ngx_config.h>
+
+#include <ngx_core.h>
+#include <ngx_types.h>
+#include <ngx_alloc.h>
+#include <ngx_array.h>
+#include <ngx_hunk.h>
+#include <ngx_connection.h>
+#include <ngx_sendv.h>
+#include <ngx_sendfile.h>
+
+
+ngx_chain_t *ngx_freebsd_write_chain(ngx_connection_t *c, ngx_chain_t *in)
+{
+    int              rc;
+    char            *prev;
+    size_t           hsize;
+    off_t            sent;
+    struct iovec    *iov;
+    struct sf_hdtr   hdtr;
+    ngx_err_t        err;
+    ngx_array_t      header, trailer;
+    ngx_hunk_t      *file;
+    ngx_chain_t     *ce;
+
+    ce = in;
+    file = NULL;
+    hsize = 0;
+
+    ngx_init_array(header, c->pool, 10, sizeof(struct iovec), NGX_CHAIN_ERROR);
+    ngx_init_array(trailer, c->pool, 10, sizeof(struct iovec), NGX_CHAIN_ERROR);
+
+    /* create the header iovec */
+    if (ce->hunk->type & NGX_HUNK_IN_MEMORY) {
+        prev = NULL;
+        iov = NULL;
+
+        /* create the iovec and coalesce the neighbouring chain entries */
+        while (ce && (ce->hunk->type & NGX_HUNK_IN_MEMORY))
+        {
+            if (prev == ce->hunk->pos.mem) {
+                iov->iov_len += ce->hunk->last.mem - ce->hunk->pos.mem;
+                prev = ce->hunk->last.mem;
+
+            } else {
+                ngx_test_null(iov, ngx_push_array(&header), NGX_CHAIN_ERROR);
+                iov->iov_base = ce->hunk->pos.mem;
+                iov->iov_len = ce->hunk->last.mem - ce->hunk->pos.mem;
+                prev = ce->hunk->last.mem;
+            }
+
+#if (HAVE_FREEBSD_SENDFILE_NBYTES_BUG)
+            hsize += ce->hunk->last.mem - ce->hunk->pos.mem;
+#endif
+            ce = ce->next;
+        }
+    }
+
+    /* TODO: coalesce the neighbouring shadow file hunks */
+    if (ce && (ce->hunk->type & NGX_HUNK_FILE)) {
+        file = ce->hunk;
+        ce = ce->next;
+    }
+
+    /* create the trailer iovec */
+    if (ce && ce->hunk->type & NGX_HUNK_IN_MEMORY) {
+        prev = NULL;
+        iov = NULL;
+
+        /* create the iovec and coalesce the neighbouring chain entries */
+        while (ce && (ce->hunk->type & NGX_HUNK_IN_MEMORY)) {
+
+            if (prev == ce->hunk->pos.mem) {
+                iov->iov_len += ce->hunk->last.mem - ce->hunk->pos.mem;
+                prev = ce->hunk->last.mem;
+
+            } else {
+                ngx_test_null(iov, ngx_push_array(&trailer), NGX_CHAIN_ERROR);
+                iov->iov_base = ce->hunk->pos.mem;
+                iov->iov_len = ce->hunk->last.mem - ce->hunk->pos.mem;
+                prev = ce->hunk->last.mem;
+            }
+
+            ce = ce->next;
+        }
+    }
+
+    if (file) {
+        hdtr.headers = (struct iovec *) header.elts;
+        hdtr.hdr_cnt = header.nelts;
+        hdtr.trailers = (struct iovec *) trailer.elts;
+        hdtr.trl_cnt = trailer.nelts;
+
+        rc = sendfile(file->file->fd, c->fd, file->pos.file,
+                      (size_t) (file->last.file - file->pos.file) + hsize,
+                      &hdtr, &sent, 0);
+
+        if (rc == -1) {
+            err = ngx_errno;
+            if (err == NGX_EAGAIN || err == NGX_EINTR) {
+                ngx_log_error(NGX_LOG_INFO, c->log, err,
+                              "sendfile() sent only %qd bytes", sent);
+
+            } else {
+                ngx_log_error(NGX_LOG_CRIT, c->log, err, "sendfile() failed");
+                return NGX_CHAIN_ERROR;
+            }
+        }
+
+#if (NGX_DEBUG_WRITE_CHAIN)
+        ngx_log_debug(c->log, "sendfile: %d, @%qd %qd:%d" _
+                      rc _ file->pos.file _ *sent _
+                      (size_t) (file->last.file - file->pos.file) + hsize);
+#endif
+
+    } else {
+        rc = writev(c->fd, (struct iovec *) header.elts, header.nelts);
+
+        if (rc == -1) {
+            err = ngx_errno;
+            if (err == NGX_EAGAIN) {
+                ngx_log_error(NGX_LOG_INFO, c->log, err, "writev() EAGAIN");
+
+            } else if (err == NGX_EINTR) {
+                ngx_log_error(NGX_LOG_INFO, c->log, err, "writev() EINTR");
+
+            } else {
+                ngx_log_error(NGX_LOG_CRIT, c->log, err, "writev() failed");
+                return NGX_CHAIN_ERROR;
+            }
+        }
+
+        sent = rc > 0 ? rc : 0;
+    }
+
+#if (NGX_DEBUG_WRITE_CHAIN)
+    ngx_log_debug(c->log, "sendv: %qd" _ sent);
+#endif
+
+    c->sent += sent;
+
+    for (ce = in; ce; ce = ce->next) {
+
+#if (NGX_DEBUG_WRITE_CHAIN)
+        ngx_log_debug(c->log, "write chain: %x %qx %qd" _
+                      ce->hunk->type _
+                      ce->hunk->pos.file _
+                      ce->hunk->last.file - ce->hunk->pos.file);
+#endif
+
+        if (sent >= ce->hunk->last.file - ce->hunk->pos.file) {
+            sent -= ce->hunk->last.file - ce->hunk->pos.file;
+            ce->hunk->pos.file = ce->hunk->last.file;
+
+#if (NGX_DEBUG_WRITE_CHAIN)
+            ngx_log_debug(c->log, "write chain done: %qx %qd" _
+                          ce->hunk->pos.file _ sent);
+#endif
+            continue;
+        }
+
+        ce->hunk->pos.file += sent;
+
+#if (NGX_DEBUG_WRITE_CHAIN)
+        ngx_log_debug(c->log, "write chain rest: %qx %qd" _
+                      ce->hunk->pos.file _
+                      ce->hunk->last.file - ce->hunk->pos.file);
+#endif
+
+        break;
+    }
+
+    ngx_destroy_array(&trailer);
+    ngx_destroy_array(&header);
+
+    return ce;
+}