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packets, pktbuf: Align L3 headers on 32-bit boundary.

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Memory access tends to be faster when data is properly aligned.

Signed-off-by: Ben Pfaff <blp@nicira.com>
This commit is contained in:
Ben Pfaff
2013-08-27 22:10:22 -07:00
parent 4528f34f93
commit bb622f82d7
4 changed files with 20 additions and 14 deletions
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20
lib/packets.c
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@@ -152,9 +152,9 @@ compose_rarp(struct ofpbuf *b, const uint8_t eth_src[ETH_ADDR_LEN])
struct arp_eth_header *arp;
ofpbuf_clear(b);
ofpbuf_prealloc_tailroom(b, ETH_HEADER_LEN + VLAN_HEADER_LEN
ofpbuf_prealloc_tailroom(b, 2 + ETH_HEADER_LEN + VLAN_HEADER_LEN
+ ARP_ETH_HEADER_LEN);
ofpbuf_reserve(b, VLAN_HEADER_LEN);
ofpbuf_reserve(b, 2 + 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);
@@ -396,13 +396,16 @@ pop_mpls(struct ofpbuf *packet, ovs_be16 ethtype)
/* Converts hex digits in 'hex' to an Ethernet packet in '*packetp'. The
* caller must free '*packetp'. On success, returns NULL. On failure, returns
* an error message and stores NULL in '*packetp'. */
* an error message and stores NULL in '*packetp'.
*
* Aligns the L3 header of '*packetp' on a 32-bit boundary. */
const char *
eth_from_hex(const char *hex, struct ofpbuf **packetp)
{
struct ofpbuf *packet;
packet = *packetp = ofpbuf_new(strlen(hex) / 2);
/* Use 2 bytes of headroom to 32-bit align the L3 header. */
packet = *packetp = ofpbuf_new_with_headroom(strlen(hex) / 2, 2);
if (ofpbuf_put_hex(packet, hex, NULL)[0] != '\0') {
ofpbuf_delete(packet);
@@ -603,7 +606,8 @@ ipv6_is_cidr(const struct in6_addr *netmask)
* '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.
* Ethernet header and payload respectively. Aligns b->l3 on a 32-bit
* boundary.
*
* The returned packet has enough headroom to insert an 802.1Q VLAN header if
* desired. */
@@ -617,8 +621,10 @@ eth_compose(struct ofpbuf *b, const uint8_t eth_dst[ETH_ADDR_LEN],
ofpbuf_clear(b);
ofpbuf_prealloc_tailroom(b, ETH_HEADER_LEN + VLAN_HEADER_LEN + size);
ofpbuf_reserve(b, VLAN_HEADER_LEN);
/* The magic 2 here ensures that the L3 header (when it is added later)
* will be 32-bit aligned. */
ofpbuf_prealloc_tailroom(b, 2 + ETH_HEADER_LEN + VLAN_HEADER_LEN + size);
ofpbuf_reserve(b, 2 + VLAN_HEADER_LEN);
eth = ofpbuf_put_uninit(b, ETH_HEADER_LEN);
data = ofpbuf_put_uninit(b, size);