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gnrc_sixlowpan_iphc: add extension header encoding

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This commit is contained in:
Martine S. Lenders 2019-12-04 20:13:04 +01:00
parent a0a334a491
commit 8ce3c745c8
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GPG Key ID: CCD317364F63286F
1 changed files with 250 additions and 32 deletions
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274
sys/net/gnrc/network_layer/sixlowpan/iphc/gnrc_sixlowpan_iphc.c
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@ -20,6 +20,7 @@
#include "byteorder.h"
#include "net/ipv6/hdr.h"
#include "net/ipv6/ext.h"
#include "net/gnrc.h"
#include "net/gnrc/netif/internal.h"
#include "net/gnrc/sixlowpan.h"
@ -96,6 +97,16 @@
#define NHC_UDP_8BIT_PORT (0xF000)
#define NHC_UDP_8BIT_MASK (0xFF00)
#define NHC_IPV6_EXT_ID (0xE0)
#define NHC_IPV6_EXT_NH (0x01)
#define NHC_IPV6_EXT_EID_HOPOPT (0x00 << 1)
#define NHC_IPV6_EXT_EID_RH (0x01 << 1)
#define NHC_IPV6_EXT_EID_FRAG (0x02 << 1)
#define NHC_IPV6_EXT_EID_DST (0x03 << 1)
#define NHC_IPV6_EXT_EID_MOB (0x04 << 1)
#define NHC_IPV6_EXT_EID_IPV6 (0x07 << 1)
/* currently only used with forwarding output, remove guard if more debug info
* is added */
#ifdef MODULE_GNRC_SIXLOWPAN_FRAG_VRB
@ -742,6 +753,24 @@ static int _forward_frag(gnrc_pktsnip_t *pkt, gnrc_pktsnip_t *frag_hdr,
}
#endif /* MODULE_GNRC_SIXLOWPAN_FRAG_VRB */
static inline bool _compressible_nh(uint8_t nh)
{
switch (nh) {
#ifdef MODULE_GNRC_SIXLOWPAN_IPHC_NHC
case PROTNUM_IPV6_EXT_HOPOPT:
case PROTNUM_UDP:
case PROTNUM_IPV6:
case PROTNUM_IPV6_EXT_RH:
case PROTNUM_IPV6_EXT_FRAG:
case PROTNUM_IPV6_EXT_DST:
case PROTNUM_IPV6_EXT_MOB:
return true;
#endif
default:
return false;
}
}
static size_t _iphc_ipv6_encode(gnrc_pktsnip_t *pkt,
const gnrc_netif_hdr_t *netif_hdr,
gnrc_netif_t *iface,
@ -823,16 +852,11 @@ static size_t _iphc_ipv6_encode(gnrc_pktsnip_t *pkt,
}
/* check for compressible next header */
switch (ipv6_hdr->nh) {
#ifdef MODULE_GNRC_SIXLOWPAN_IPHC_NHC
case PROTNUM_UDP:
if (_compressible_nh(ipv6_hdr->nh)) {
iphc_hdr[IPHC1_IDX] |= SIXLOWPAN_IPHC1_NH;
break;
#endif
default:
}
else {
iphc_hdr[inline_pos++] = ipv6_hdr->nh;
break;
}
/* compress hop limit */
@ -1031,6 +1055,85 @@ static size_t _iphc_ipv6_encode(gnrc_pktsnip_t *pkt,
}
#ifdef MODULE_GNRC_SIXLOWPAN_IPHC_NHC
static ssize_t _iphc_nhc_ipv6_ext_encode(uint8_t *nhc_data,
const gnrc_pktsnip_t *ext,
uint16_t ext_len,
uint8_t *protnum)
{
const ipv6_ext_t *ext_hdr = ext->data;
size_t nhc_len = 1; /* skip over NHC header */
uint8_t nh = ext_hdr->nh;
/* From https://tools.ietf.org/html/rfc6282#section-4.1:
* > The Length field contained in a compressed IPv6 Extension Header
* > indicates the number of octets that pertain to the (compressed)
* > extension header following the Length field.
*
* ipv6_ext_t is nh + length field so subtract it
*/
ext_len -= sizeof(ipv6_ext_t);
if (ext_len > UINT8_MAX) {
/* From https://tools.ietf.org/html/rfc6282#section-4.1:
* > Note that specifying units in octets means that LOWPAN_NHC MUST NOT
* > be used to encode IPv6 Extension Headers that have more than 255
* > octets following the Length field after compression. */
return 0;
}
/* Set IPv6 extension compression header type
* (see https://tools.ietf.org/html/rfc6282#section-4.2). */
nhc_data[0] = NHC_IPV6_EXT_ID;
switch (*protnum) {
case PROTNUM_IPV6_EXT_HOPOPT:
nhc_data[0] |= NHC_IPV6_EXT_EID_HOPOPT;
/* TODO: decrement ext_len by length of trailing Pad1/PadN option:
* > IPv6 Hop-by-Hop and Destination Options Headers may use a trailing
* > Pad1 or PadN to achieve 8-octet alignment. When there is a single
* > trailing Pad1 or PadN option of 7 octets or less and the containing
* > header is a multiple of 8 octets, the trailing Pad1 or PadN option
* > MAY be elided by the compressor. */
break;
case PROTNUM_IPV6_EXT_RH:
nhc_data[0] |= NHC_IPV6_EXT_EID_RH;
break;
case PROTNUM_IPV6_EXT_FRAG:
nhc_data[0] |= NHC_IPV6_EXT_EID_FRAG;
break;
case PROTNUM_IPV6_EXT_DST:
nhc_data[0] |= NHC_IPV6_EXT_EID_DST;
/* TODO: decrement ext_len by length of trailing Pad1/PadN option:
* > IPv6 Hop-by-Hop and Destination Options Headers may use a trailing
* > Pad1 or PadN to achieve 8-octet alignment. When there is a single
* > trailing Pad1 or PadN option of 7 octets or less and the containing
* > header is a multiple of 8 octets, the trailing Pad1 or PadN option
* > MAY be elided by the compressor. */
break;
case PROTNUM_IPV6_EXT_MOB:
nhc_data[0] |= NHC_IPV6_EXT_EID_MOB;
break;
default:
return -1;
}
if (_compressible_nh(nh) &&
/* carry next header inline when fragment header and offset is equal to
* 0 (which means the next header indicates the next header after the
* fragment header in the *first fragment*) */
((*protnum != PROTNUM_IPV6_EXT_FRAG) ||
(ipv6_ext_frag_get_offset((ipv6_ext_frag_t *)ext_hdr) == 0))) {
nhc_data[0] |= NHC_IPV6_EXT_NH;
}
else {
nhc_data[nhc_len++] = ext_hdr->nh;
/* prevent next header from being encoded regardless (e.g. if not
* first IPv6 fragment) */
nh = PROTNUM_RESERVED;
}
/* integer overflow prevented by `ext_len > UINT8_MAX` check above */
nhc_data[nhc_len++] = (uint8_t)ext_len;
memcpy(&nhc_data[nhc_len], ext_hdr + 1, ext_len);
*protnum = nh;
return nhc_len + ext_len;
}
static inline size_t iphc_nhc_udp_encode(uint8_t *nhc_data,
const gnrc_pktsnip_t *udp)
{
@ -1079,6 +1182,99 @@ static inline size_t iphc_nhc_udp_encode(uint8_t *nhc_data,
return nhc_len;
}
static bool _remove_header(gnrc_pktsnip_t *pkt, gnrc_pktsnip_t *hdr,
size_t exp_hdr_size)
{
if (hdr->size > exp_hdr_size) {
hdr = gnrc_pktbuf_mark(hdr, exp_hdr_size,
GNRC_NETTYPE_UNDEF);
if (hdr == NULL) {
DEBUG("6lo iphc: unable to remove compressed header\n");
return false;
}
}
gnrc_pktbuf_remove_snip(pkt, hdr);
return true;
}
static ssize_t _nhc_ipv6_encode_snip(gnrc_pktsnip_t *pkt,
const gnrc_netif_hdr_t *netif_hdr,
gnrc_netif_t *iface,
uint8_t *nhc_data,
uint8_t *nh)
{
gnrc_pktsnip_t *hdr = pkt->next->next;
ssize_t nhc_len = 1; /* skip over NHC header */
size_t tmp;
uint8_t new_nh = ((ipv6_hdr_t *)hdr->data)->nh;
assert(hdr->size >= sizeof(ipv6_hdr_t));
/* Set IPv6 extension compression header type
* (see https://tools.ietf.org/html/rfc6282#section-4.2). */
nhc_data[0] = NHC_IPV6_EXT_ID;
if (_compressible_nh(new_nh)) {
nhc_data[0] |= NHC_IPV6_EXT_NH;
}
else {
nhc_data[nhc_len++] = new_nh;
}
/* save to cast as result is max 40 */
tmp = (ssize_t)_iphc_ipv6_encode(hdr, netif_hdr, iface, &nhc_data[nhc_len]);
if (tmp == 0) {
DEBUG("6lo iphc: error encoding IPv6 header\n");
return -1;
}
nhc_len += tmp;
/* remove encapsulated IPv6 header */
if (!_remove_header(pkt, hdr, sizeof(ipv6_hdr_t))) {
return -1;
}
*nh = new_nh;
return nhc_len;
}
static ssize_t _nhc_ipv6_ext_encode_snip(gnrc_pktsnip_t *pkt, uint8_t *nhc_data,
uint8_t *nh)
{
gnrc_pktsnip_t *hdr = pkt->next->next;
ipv6_ext_t *ext = hdr->data;
ssize_t nhc_len;
uint16_t ext_len = ((ext->len * IPV6_EXT_LEN_UNIT) + IPV6_EXT_LEN_UNIT);
uint8_t new_nh = *nh;
assert((hdr->size >= sizeof(ipv6_ext_t)) && (hdr->size >= ext_len));
/* _iphc_nhc_ipv6_ext_encode() manipulates nh, so use `new_nh` as temporary
* carrier in case of later errors */
nhc_len = _iphc_nhc_ipv6_ext_encode(nhc_data, hdr, ext_len, &new_nh);
if (nhc_len == 0) {
/* extension header is not compressible, so don't compress it and
* just copy it after the preceding compression headers */
return nhc_len;
}
/* remove IPv6 extension header */
if (!_remove_header(pkt, hdr, ext_len)) {
return -1;
}
*nh = new_nh;
return nhc_len;
}
static ssize_t _nhc_udp_encode_snip(gnrc_pktsnip_t *pkt, uint8_t *nhc_data)
{
gnrc_pktsnip_t *hdr = pkt->next->next;
ssize_t nhc_len;
assert(hdr->size >= sizeof(udp_hdr_t));
/* save to cast, as result is max 8 */
nhc_len = (ssize_t)iphc_nhc_udp_encode(nhc_data, hdr);
/* remove UDP header */
if (!_remove_header(pkt, hdr, sizeof(udp_hdr_t))) {
return -1;
}
return nhc_len;
}
#endif
static inline bool _compressible(gnrc_pktsnip_t *hdr)
@ -1086,8 +1282,13 @@ static inline bool _compressible(gnrc_pktsnip_t *hdr)
switch (hdr->type) {
case GNRC_NETTYPE_UNDEF: /* when forwarded */
case GNRC_NETTYPE_IPV6:
#if defined(MODULE_GNRC_SIXLOWPAN_IPHC_NHC) && defined(MODULE_GNRC_UDP)
#if defined(MODULE_GNRC_SIXLOWPAN_IPHC_NHC)
# if defined(MODULE_GNRC_IPV6_EXT)
case GNRC_NETTYPE_IPV6_EXT:
# endif /* defined(MODULE_GNRC_IPV6_EXT) */
# if defined(MODULE_GNRC_UDP)
case GNRC_NETTYPE_UDP:
# endif /* defined(MODULE_GNRC_UDP) */
#endif
return true;
default:
@ -1141,7 +1342,7 @@ static gnrc_pktsnip_t *_iphc_encode(gnrc_pktsnip_t *pkt,
/* there should be at least one compressible header in `pkt`, otherwise this
* function should not be called */
assert(dispatch_size > 0);
dispatch = gnrc_pktbuf_add(NULL, NULL, dispatch_size,
dispatch = gnrc_pktbuf_add(NULL, NULL, dispatch_size + 1,
GNRC_NETTYPE_SIXLOWPAN);
if (dispatch == NULL) {
@ -1154,33 +1355,50 @@ static gnrc_pktsnip_t *_iphc_encode(gnrc_pktsnip_t *pkt,
if (inline_pos == 0) {
DEBUG("6lo iphc: error encoding IPv6 header\n");
gnrc_pktbuf_release(dispatch);
return NULL;
}
nh = ((ipv6_hdr_t *)pkt->next->data)->nh;
#ifdef MODULE_GNRC_SIXLOWPAN_IPHC_NHC
while (_compressible_nh(nh)) {
ssize_t local_pos = 0;
switch (nh) {
case PROTNUM_UDP: {
gnrc_pktsnip_t *udp = pkt->next->next;
assert(udp->size >= sizeof(udp_hdr_t));
inline_pos += iphc_nhc_udp_encode(&iphc_hdr[inline_pos], udp);
/* remove UDP header */
if (udp->size > sizeof(udp_hdr_t)) {
udp = gnrc_pktbuf_mark(udp, sizeof(udp_hdr_t),
GNRC_NETTYPE_UNDEF);
if (udp == NULL) {
DEBUG("gnrc_sixlowpan_iphc_encode: unable to mark UDP header\n");
case PROTNUM_UDP:
local_pos = _nhc_udp_encode_snip(pkt, &iphc_hdr[inline_pos]);
/* abort loop on next iteration */
nh = PROTNUM_RESERVED;
break;
case PROTNUM_IPV6: { /* encapsulated IPv6 header */
local_pos = _nhc_ipv6_encode_snip(pkt, netif_hdr, iface,
&iphc_hdr[inline_pos], &nh);
break;
}
case PROTNUM_IPV6_EXT_HOPOPT:
case PROTNUM_IPV6_EXT_RH:
case PROTNUM_IPV6_EXT_FRAG:
case PROTNUM_IPV6_EXT_DST:
case PROTNUM_IPV6_EXT_MOB:
local_pos = _nhc_ipv6_ext_encode_snip(pkt,
&iphc_hdr[inline_pos],
&nh);
if (local_pos == 0) {
/* abort loop, extension header is not compressible as
* length field is too large value */
nh = PROTNUM_RESERVED;
}
break;
default:
/* abort loop on next iteration */
nh = PROTNUM_RESERVED;
break;
}
if (local_pos < 0) {
DEBUG("6lo iphc: error on compressing next header\n");
gnrc_pktbuf_release(dispatch);
return NULL;
}
}
gnrc_pktbuf_remove_snip(pkt, udp);
break;
}
default:
break;
inline_pos += local_pos;
}
#endif