gnrc_ipv6_ext_opt: initial import

This provides header parsing for IPv6 hop-by-hop and destination
options according to [RFC 8200].

[RFC 8200]: https://tools.ietf.org/html/rfc8200#section-4.2

Makefile.dep

@@ -300,6 +300,10 @@ ifneq (,$(filter gnrc_ipv6_ext_frag,$(USEMODULE)))
   USEMODULE += xtimer
 endif
 
+ifneq (,$(filter gnrc_ipv6_ext_opt,$(USEMODULE)))
+  USEMODULE += gnrc_ipv6_ext
+endif
+
 ifneq (,$(filter gnrc_ipv6_ext_rh,$(USEMODULE)))
   USEMODULE += gnrc_ipv6_ext
 endif

sys/include/net/gnrc/ipv6/ext/opt.h

@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2020 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    net_gnrc_ipv6_ext_opt Support for IPv6 option extension headers
+ * @ingroup     net_gnrc_ipv6_ext
+ * @brief       GNRC implementation of IPv6 hop-by-hop and destination option
+ *              header extension
+ * @{
+ *
+ * @file
+ * @brief   GNRC hop-by-hop and destination option header definitions.
+ *
+ * @author  Martine Lenders <m.lenders@fu-berlin.de>
+ */
+#ifndef NET_GNRC_IPV6_EXT_OPT_H
+#define NET_GNRC_IPV6_EXT_OPT_H
+
+#include <stdint.h>
+
+#include "net/gnrc/pkt.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Processes all options within an IPv6 option header
+ *
+ * @pre `pkt != NULL`
+ * @pre `(protnum == PROTNUM_IPV6_EXT_HOPOPT) || (protnum == PROTNUM_IPV6_EXT_DST)`
+ *
+ * @param[in] pkt       The packet containing the option header. The option
+ *                      must be contained in the first snip, with all
+ *                      preceding headers marked (in receive order).
+ *                      Must not be NULL.
+ * @param[in] protnum   The protocol number of the option header. Must be
+ *                      @ref PROTNUM_IPV6_EXT_HOPOPT or @ref
+ *                      PROTNUM_IPV6_EXT_DST
+ *
+ * @return  @p pkt with the option header marked on success.
+ * @return  NULL, if the packet was consumed by the option handling.
+ * @return  NULL, on error. @p pkt is released with EINVAL in that case and if
+ *          necessary and [`gnrc_icmpv6_error`](@ref net_gnrc_icmpv6_error) is
+ *          used, the according ICMPv6 error message is sent.
+ */
+gnrc_pktsnip_t *gnrc_ipv6_ext_opt_process(gnrc_pktsnip_t *pkt,
+                                          uint8_t protnum);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NET_GNRC_IPV6_EXT_OPT_H */
+/** @} */

sys/net/gnrc/Makefile

@@ -19,6 +19,9 @@ endif
 ifneq (,$(filter gnrc_ipv6_ext_frag,$(USEMODULE)))
   DIRS += network_layer/ipv6/ext/frag
 endif
+ifneq (,$(filter gnrc_ipv6_ext_opt,$(USEMODULE)))
+  DIRS += network_layer/ipv6/ext/opt
+endif
 ifneq (,$(filter gnrc_ipv6_ext_rh,$(USEMODULE)))
   DIRS += network_layer/ipv6/ext/rh
 endif

sys/net/gnrc/network_layer/ipv6/ext/gnrc_ipv6_ext.c

@@ -24,6 +24,7 @@
 #include "net/gnrc/icmpv6/error.h"
 #include "net/gnrc/ipv6.h"
 #include "net/gnrc/ipv6/ext/frag.h"
+#include "net/gnrc/ipv6/ext/opt.h"
 #include "net/gnrc/ipv6/ext/rh.h"
 #if defined(MODULE_GNRC_SIXLOWPAN_IPHC_NHC) && \
     defined(MODULE_GNRC_IPV6_EXT_FRAG)
@@ -311,6 +312,10 @@ static gnrc_pktsnip_t *_demux(gnrc_pktsnip_t *pkt, unsigned protnum)
 #endif  /* MODULE_GNRC_IPV6_EXT_FRAG */
         case PROTNUM_IPV6_EXT_HOPOPT:
         case PROTNUM_IPV6_EXT_DST:
+            if (IS_USED(MODULE_GNRC_IPV6_EXT_OPT)) {
+                return gnrc_ipv6_ext_opt_process(pkt, protnum);
+            }
+            /* Intentionally falls through */
         case PROTNUM_IPV6_EXT_AH:
         case PROTNUM_IPV6_EXT_ESP:
         case PROTNUM_IPV6_EXT_MOB:

sys/net/gnrc/network_layer/ipv6/ext/opt/Makefile

@@ -0,0 +1,3 @@
+MODULE := gnrc_ipv6_ext_opt
+
+include $(RIOTBASE)/Makefile.base

sys/net/gnrc/network_layer/ipv6/ext/opt/gnrc_ipv6_ext_opt.c

@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2020 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ * @author  Martine Lenders <m.lenders@fu-berlin.de>
+ */
+
+#include "net/ipv6.h"
+#include "net/ipv6/ext.h"
+#include "net/ipv6/ext/opt.h"
+#include "net/gnrc/icmpv6/error.h"
+#include "net/gnrc/pktbuf.h"
+
+#include "net/gnrc/ipv6/ext/opt.h"
+
+#define ENABLE_DEBUG    (0)
+#include "debug.h"
+
+/**
+ * @brief   Determine what action to do, when option is not recognized
+ *
+ * @see     https://tools.ietf.org/html/rfc8200#section-4.2
+ *
+ * @param[in] type  Type of the option
+ */
+static inline uint8_t _unrec_action(uint8_t type)
+{
+    return (type & IPV6_EXT_OPT_ACTION_MASK);
+}
+
+static bool _multicast_dst(gnrc_pktsnip_t *pkt)
+{
+    gnrc_pktsnip_t *ipv6 = gnrc_pktsnip_search_type(pkt, GNRC_NETTYPE_IPV6);
+    ipv6_hdr_t *ipv6_hdr;
+
+    assert(ipv6 != NULL);
+    ipv6_hdr = ipv6->data;
+    return ipv6_addr_is_multicast(&ipv6_hdr->dst);
+}
+
+gnrc_pktsnip_t *gnrc_ipv6_ext_opt_process(gnrc_pktsnip_t *pkt,
+                                          uint8_t protnum)
+{
+    assert(pkt != NULL);
+    assert((protnum == PROTNUM_IPV6_EXT_HOPOPT) ||
+           (protnum == PROTNUM_IPV6_EXT_DST));
+    gnrc_pktsnip_t *hdr;
+    ipv6_ext_t *opt_hdr = pkt->data;
+    uint8_t *opts;
+    size_t hdr_len;
+
+    if (pkt->size < sizeof(ipv6_ext_t)) {
+        DEBUG("gnrc_ipv6_ext_opt: packet of invalid size\n");
+        goto error;
+    }
+    hdr_len = ((opt_hdr->len * IPV6_EXT_LEN_UNIT) + IPV6_EXT_LEN_UNIT);
+    hdr = gnrc_pktbuf_mark(pkt, hdr_len, GNRC_NETTYPE_IPV6_EXT);
+    if (hdr == NULL) {
+        DEBUG("gnrc_ipv6_ext_opt: unable to mark option header\n");
+        goto error;
+    }
+    opts = hdr->data;
+    for (unsigned offset = sizeof(ipv6_ext_t); offset < hdr_len;) {
+        uint8_t opt_type = opts[offset++];
+        uint8_t opt_len;
+
+        if (opt_type == IPV6_EXT_OPT_PAD1) {
+            /* nothing more to do */
+            continue;
+        }
+        opt_len = opts[offset++];
+        if (opt_len > (hdr_len - offset)) {
+            DEBUG("gnrc_ipv6_ext_opt: invalid option size\n");
+            goto error;
+        }
+        switch (opt_type) {
+            /* IPV6_EXT_OPT_PAD1 already handled before length check due
+             * to special format */
+            case IPV6_EXT_OPT_PADN:
+                /* nothing to do, offset will be progressed below */
+                break;
+            default: {
+                bool send_error = false;
+
+                switch (_unrec_action(opt_type)) {
+                    case IPV6_EXT_OPT_ACTION_SKIP:
+                        DEBUG("gnrc_ipv6_ext_opt: skipping unknown "
+                              "option %02x\n", opt_type);
+                        /* skip here already, as we don't reach the
+                         * incrementation of offset below */
+                        offset += opt_len;
+                        continue;
+                    case IPV6_EXT_OPT_ACTION_DISC:
+                        break;
+                    case IPV6_EXT_OPT_ACTION_DISC_ERR_MCAST:
+                        send_error = IS_USED(MODULE_GNRC_ICMPV6_ERROR);
+                        break;
+                    case IPV6_EXT_OPT_ACTION_DISC_ERR:
+                        send_error = IS_USED(MODULE_GNRC_ICMPV6_ERROR) &&
+                                     !_multicast_dst(pkt);
+                        break;
+                }
+                DEBUG("gnrc_ipv6_ext_opt: discarding packet with unknown "
+                      "option %02x\n", opt_type);
+                if (send_error) {
+                    DEBUG("gnrc_ipv6_ext_opt: reporting parameter problem "
+                          "for option %02x (pos at %02x)\n", opts[offset - 2U],
+                          opt_type);
+                    gnrc_icmpv6_error_param_prob_send(
+                            ICMPV6_ERROR_PARAM_PROB_OPT,
+                            /* offset was already progressed to opt data*/
+                            &opts[offset - 2U], pkt);
+                }
+                goto error;
+            }
+        }
+        offset += opt_len;
+    }
+    return pkt;
+error:
+    gnrc_pktbuf_release_error(pkt, EINVAL);
+    return NULL;
+}
+
+/** @} */