/* Creates and returns a new ofpbuf with an initial capacity of 'size +
* headroom' bytes, reserving the first 'headroom' bytes as headroom. */
struct ofpbuf *
ofpbuf_new_with_headroom(size_t size, size_t headroom)
{
struct ofpbuf *b = ofpbuf_new(size + headroom);
ofpbuf_reserve(b, headroom);
return b;
}
/* Populates 'b' with an Ethernet LLC+SNAP packet headed with the given
* 'eth_dst', 'eth_src', 'snap_org', and 'snap_type'. A payload of 'size'
* bytes is allocated in 'b' and returned. This payload may be populated with
* appropriate information by the caller.
*
* The returned packet has enough headroom to insert an 802.1Q VLAN header if
* desired. */
void *
snap_compose(struct ofpbuf *b, const uint8_t eth_dst[ETH_ADDR_LEN],
const uint8_t eth_src[ETH_ADDR_LEN],
unsigned int oui, uint16_t snap_type, size_t size)
{
struct eth_header *eth;
struct llc_snap_header *llc_snap;
void *payload;
/* Compose basic packet structure. (We need the payload size to stick into
* the 802.2 header.) */
ofpbuf_clear(b);
ofpbuf_prealloc_tailroom(b, ETH_HEADER_LEN + VLAN_HEADER_LEN
+ LLC_SNAP_HEADER_LEN + size);
ofpbuf_reserve(b, VLAN_HEADER_LEN);
eth = ofpbuf_put_zeros(b, ETH_HEADER_LEN);
llc_snap = ofpbuf_put_zeros(b, LLC_SNAP_HEADER_LEN);
payload = ofpbuf_put_uninit(b, size);
/* Compose 802.2 header. */
memcpy(eth->eth_dst, eth_dst, ETH_ADDR_LEN);
memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
eth->eth_type = htons(b->size - ETH_HEADER_LEN);
/* Compose LLC, SNAP headers. */
llc_snap->llc.llc_dsap = LLC_DSAP_SNAP;
llc_snap->llc.llc_ssap = LLC_SSAP_SNAP;
llc_snap->llc.llc_cntl = LLC_CNTL_SNAP;
llc_snap->snap.snap_org[0] = oui >> 16;
llc_snap->snap.snap_org[1] = oui >> 8;
llc_snap->snap.snap_org[2] = oui;
llc_snap->snap.snap_type = htons(snap_type);
return payload;
}
/* Fills 'b' with a Reverse ARP packet with Ethernet source address 'eth_src'.
* This function is used by Open vSwitch to compose packets in cases where
* context is important but content doesn't (or shouldn't) matter.
*
* The returned packet has enough headroom to insert an 802.1Q VLAN header if
* desired. */
void
compose_rarp(struct ofpbuf *b, const uint8_t eth_src[ETH_ADDR_LEN])
{
struct eth_header *eth;
struct rarp_header *rarp;
ofpbuf_clear(b);
ofpbuf_prealloc_tailroom(b, ETH_HEADER_LEN + VLAN_HEADER_LEN
+ RARP_HEADER_LEN);
ofpbuf_reserve(b, VLAN_HEADER_LEN);
eth = ofpbuf_put_uninit(b, sizeof *eth);
memcpy(eth->eth_dst, eth_addr_broadcast, ETH_ADDR_LEN);
memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
eth->eth_type = htons(ETH_TYPE_RARP);
rarp = ofpbuf_put_uninit(b, sizeof *rarp);
rarp->hw_addr_space = htons(ARP_HTYPE_ETH);
rarp->proto_addr_space = htons(ETH_TYPE_IP);
rarp->hw_addr_length = ETH_ADDR_LEN;
rarp->proto_addr_length = sizeof rarp->src_proto_addr;
rarp->opcode = htons(RARP_REQUEST_REVERSE);
memcpy(rarp->src_hw_addr, eth_src, ETH_ADDR_LEN);
rarp->src_proto_addr = htonl(0);
memcpy(rarp->target_hw_addr, eth_src, ETH_ADDR_LEN);
rarp->target_proto_addr = htonl(0);
}
/* Populates 'b' with an Ethernet II packet headed with the given 'eth_dst',
* 'eth_src' and 'eth_type' parameters. A payload of 'size' bytes is allocated
* in 'b' and returned. This payload may be populated with appropriate
* information by the caller. Sets 'b''s 'l2' and 'l3' pointers to the
* Ethernet header and payload respectively.
*
* The returned packet has enough headroom to insert an 802.1Q VLAN header if
* desired. */
void *
eth_compose(struct ofpbuf *b, const uint8_t eth_dst[ETH_ADDR_LEN],
const uint8_t eth_src[ETH_ADDR_LEN], uint16_t eth_type,
size_t size)
{
void *data;
struct eth_header *eth;
ofpbuf_clear(b);
ofpbuf_prealloc_tailroom(b, ETH_HEADER_LEN + VLAN_HEADER_LEN + size);
ofpbuf_reserve(b, VLAN_HEADER_LEN);
eth = ofpbuf_put_uninit(b, ETH_HEADER_LEN);
data = ofpbuf_put_uninit(b, size);
memcpy(eth->eth_dst, eth_dst, ETH_ADDR_LEN);
memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
eth->eth_type = htons(eth_type);
b->l2 = eth;
b->l3 = data;
return data;
}
