@@ -1794,6 +1794,19 @@ do_deferred_options (struct context *c, const unsigned int found)

       msg (D_PUSH, "OPTIONS IMPORT: peer-id set");

       c->c2.tls_multi->use_peer_id = true;

       c->c2.tls_multi->peer_id = c->options.peer_id;

+      frame_add_to_extra_frame(&c->c2.frame, +3);	/* peer-id overhead */

+      if ( !c->options.ce.link_mtu_defined )

+	{

+	  frame_add_to_link_mtu(&c->c2.frame, +3);

+	  msg (D_PUSH, "OPTIONS IMPORT: adjusting link_mtu to %d",

+				EXPANDED_SIZE(&c->c2.frame));

+	}

+      else

+	{

+	  msg (M_WARN, "OPTIONS IMPORT: WARNING: peer-id set, but link-mtu"

+                       " fixed by config - reducing tun-mtu to %d, expect"

+                       " MTU problems", TUN_MTU_SIZE(&c->c2.frame) );

+	}

     }

 #endif

 }

@@ -2403,6 +2416,17 @@ do_init_frame (struct context *c)

 #endif

 #endif /* USE_COMP */

+  /* packets with peer-id (P_DATA_V2) need 3 extra bytes in frame (on client)

+   * and need link_mtu+3 bytes on socket reception (on server).

+   *

+   * accomodate receive path in f->extra_link, which has the side effect of

+   * also increasing send buffers (BUF_SIZE() macro), which need to be

+   * allocated big enough before receiving peer-id option from server.

+   *

+   * f->extra_frame is adjusted when peer-id option is push-received

+   */

+  frame_add_to_extra_link(&c->c2.frame, 3);

+

 #ifdef ENABLE_FRAGMENT

   /*

    * Set frame parameter for fragment code.  This is necessary because

@@ -258,6 +258,12 @@ frame_headroom (const struct frame *f, const unsigned int flag_mask)

  */

 static inline void

+frame_add_to_link_mtu (struct frame *frame, const int increment)

+{

+  frame->link_mtu += increment;

+}

+

+static inline void

 frame_add_to_extra_frame (struct frame *frame, const int increment)

 {

   frame->extra_frame += increment;

@@ -264,14 +264,16 @@ tls_get_cipher_name_pair (const char * cipher_name, size_t len) {

   return NULL;

 }

-/**

- * Max number of bytes we will add for data structures common to both data and

- * control channel packets (1 byte opcode + 3 bytes peer-id).

+/*

+ * Max number of bytes we will add

+ * for data structures common to both

+ * data and control channel packets.

+ * (opcode only).

  */

 void

 tls_adjust_frame_parameters(struct frame *frame)

 {

-  frame_add_to_extra_frame (frame, 1 + 3); /* space for opcode + peer-id */

+  frame_add_to_extra_frame (frame, 1); /* space for opcode */

 }

 /*