gnrc_sixlowpan_frag_rb: add handling for RFRAG packets

sys/net/gnrc/network_layer/sixlowpan/frag/rb/gnrc_sixlowpan_frag_rb.c

@@ -29,6 +29,7 @@
 #include "net/gnrc/sixlowpan/frag/minfwd.h"
 #include "net/gnrc/sixlowpan/frag/vrb.h"
 #include "net/sixlowpan.h"
+#include "net/sixlowpan/sfr.h"
 #include "thread.h"
 #include "xtimer.h"
 #include "utlist.h"
@@ -205,9 +206,18 @@ static gnrc_sixlowpan_frag_rb_t *_rbuf_get_by_tag(const gnrc_netif_hdr_t *netif_
 #ifndef NDEBUG
 static bool _valid_offset(gnrc_pktsnip_t *pkt, size_t offset)
 {
-    return (sixlowpan_frag_1_is(pkt->data) && (offset == 0)) ||
+    return (
-           (sixlowpan_frag_n_is(pkt->data) &&
+        IS_USED(MODULE_GNRC_SIXLOWPAN_FRAG) &&
-            (offset == sixlowpan_frag_offset(pkt->data)));
+        ((sixlowpan_frag_1_is(pkt->data) && (offset == 0)) ||
+         (sixlowpan_frag_n_is(pkt->data) &&
+          (offset == sixlowpan_frag_offset(pkt->data))))
+    ) || (
+        IS_USED(MODULE_GNRC_SIXLOWPAN_FRAG_SFR) &&
+        /* offset == 0 is an abort condition that should not be handed to the
+         * reassembly buffer */
+        sixlowpan_sfr_rfrag_is(pkt->data) &&
+        (sixlowpan_sfr_rfrag_get_offset(pkt->data) != 0)
+    );
 }
 #endif
 
@@ -239,6 +249,25 @@ static size_t _6lo_frag_size(gnrc_pktsnip_t *pkt, size_t offset, uint8_t *data)
     return frag_size;
 }
 
+static uint16_t _6lo_sfr_datagram_size(gnrc_pktsnip_t *pkt, size_t offset)
+{
+    /* offset doubles as datagram size in RFRAG header when sequence number is 0
+     * see https://tools.ietf.org/html/draft-ietf-6lo-fragment-recovery-08#section-5.1 */
+    return (offset == 0) ? sixlowpan_sfr_rfrag_get_offset(pkt->data) : 0;
+}
+
+static uint8_t *_6lo_sfr_payload(gnrc_pktsnip_t *pkt)
+{
+    return ((uint8_t *)pkt->data) + sizeof(sixlowpan_sfr_rfrag_t);
+}
+
+static size_t _6lo_sfr_frag_size(gnrc_pktsnip_t *pkt)
+{
+    /* TODO: if necessary check MAC layer here,
+     * see https://tools.ietf.org/html/draft-ietf-6lo-fragment-recovery-08#section-5.1 */
+    return sixlowpan_sfr_rfrag_get_frag_size(pkt->data);
+}
+
 static int _rbuf_add(gnrc_netif_hdr_t *netif_hdr, gnrc_pktsnip_t *pkt,
                      size_t offset, unsigned page)
 {
@@ -249,18 +278,37 @@ static int _rbuf_add(gnrc_netif_hdr_t *netif_hdr, gnrc_pktsnip_t *pkt,
     } entry;
     const uint8_t *src = gnrc_netif_hdr_get_src_addr(netif_hdr);
     const uint8_t *dst = gnrc_netif_hdr_get_dst_addr(netif_hdr);
-    uint8_t *data;
+    uint8_t *data = NULL;
-    size_t frag_size;
+    size_t frag_size = 0;   /* assign 0, otherwise cppcheck complains ;-) */
     int res;
     uint16_t datagram_size;
     uint16_t datagram_tag;
 
     /* check if provided offset is the same as in fragment */
     assert(_valid_offset(pkt, offset));
-    data = _6lo_frag_payload(pkt);
+    if (IS_USED(MODULE_GNRC_SIXLOWPAN_FRAG) && sixlowpan_frag_is(pkt->data)) {
-    frag_size = _6lo_frag_size(pkt, offset, data);
+        data = _6lo_frag_payload(pkt);
-    datagram_size = sixlowpan_frag_datagram_size(pkt->data);
+        frag_size = _6lo_frag_size(pkt, offset, data);
-    datagram_tag = sixlowpan_frag_datagram_tag(pkt->data);
+        datagram_size = sixlowpan_frag_datagram_size(pkt->data);
+        datagram_tag = sixlowpan_frag_datagram_tag(pkt->data);
+    }
+    else if (IS_USED(MODULE_GNRC_SIXLOWPAN_FRAG_SFR) &&
+             sixlowpan_sfr_rfrag_is(pkt->data)) {
+        sixlowpan_sfr_rfrag_t *rfrag = pkt->data;;
+
+        data = _6lo_sfr_payload(pkt);
+        frag_size = _6lo_sfr_frag_size(pkt);
+        /* offset doubles as datagram size in RFRAG header when sequence number
+         * is 0 */
+        datagram_size = _6lo_sfr_datagram_size(pkt, offset);
+        datagram_tag = rfrag->base.tag;
+    }
+    else {
+        /* either one of the if branches above was taken */
+        assert(data != NULL);
+        gnrc_pktbuf_release(pkt);
+        return RBUF_ADD_ERROR;
+    }
 
     gnrc_sixlowpan_frag_rb_gc();
     /* only check VRB for subsequent frags, first frags create and not get VRB