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packets: New packet_set_*() helper functions.

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This commit pulls code used to modify L3 and L4 header fields
from dp_netdev into the packet library.  An additional user will
be added in a future commit.

Signed-off-by: Ethan Jackson <ethan@nicira.com>
This commit is contained in:
Ethan Jackson
2011-12-15 17:58:23 -08:00
parent 65120a8a4e
commit c97664b30f
3 changed files with 116 additions and 109 deletions
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101
lib/packets.c
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@@ -22,6 +22,7 @@
#include <netinet/in.h>
#include <stdlib.h>
#include "byte-order.h"
#include "csum.h"
#include "dynamic-string.h"
#include "ofpbuf.h"
@@ -377,3 +378,103 @@ snap_compose(struct ofpbuf *b, const uint8_t eth_dst[ETH_ADDR_LEN],
return payload;
}
static void
packet_set_ipv4_addr(struct ofpbuf *packet, ovs_be32 *addr, ovs_be32 new_addr)
{
struct ip_header *nh = packet->l3;
if (nh->ip_proto == IPPROTO_TCP && packet->l7) {
struct tcp_header *th = packet->l4;
th->tcp_csum = recalc_csum32(th->tcp_csum, *addr, new_addr);
} else if (nh->ip_proto == IPPROTO_UDP && packet->l7) {
struct udp_header *uh = packet->l4;
if (uh->udp_csum) {
uh->udp_csum = recalc_csum32(uh->udp_csum, *addr, new_addr);
if (!uh->udp_csum) {
uh->udp_csum = htons(0xffff);
}
}
}
nh->ip_csum = recalc_csum32(nh->ip_csum, *addr, new_addr);
*addr = new_addr;
}
/* Modifies the IPv4 header fields of 'packet' to be consistent with 'src',
* 'dst', 'tos', and 'ttl'. Updates 'packet''s L4 checksums as appropriate.
* 'packet' must contain a valid IPv4 packet with correctly populated l[347]
* markers. */
void
packet_set_ipv4(struct ofpbuf *packet, ovs_be32 src, ovs_be32 dst,
uint8_t tos, uint8_t ttl)
{
struct ip_header *nh = packet->l3;
if (nh->ip_src != src) {
packet_set_ipv4_addr(packet, &nh->ip_src, src);
}
if (nh->ip_dst != dst) {
packet_set_ipv4_addr(packet, &nh->ip_dst, dst);
}
if (nh->ip_tos != tos) {
uint8_t *field = &nh->ip_tos;
nh->ip_csum = recalc_csum16(nh->ip_csum, htons((uint16_t) *field),
htons((uint16_t) tos));
*field = tos;
}
if (nh->ip_ttl != ttl) {
uint8_t *field = &nh->ip_ttl;
nh->ip_csum = recalc_csum16(nh->ip_csum, htons(*field << 8),
htons(ttl << 8));
*field = ttl;
}
}
static void
packet_set_port(ovs_be16 *port, ovs_be16 new_port, ovs_be16 *csum)
{
if (*port != new_port) {
*csum = recalc_csum16(*csum, *port, new_port);
*port = new_port;
}
}
/* Sets the TCP source and destination port ('src' and 'dst' respectively) of
* the TCP header contained in 'packet'. 'packet' must be a valid TCP packet
* with its l4 marker properly populated. */
void
packet_set_tcp_port(struct ofpbuf *packet, ovs_be16 src, ovs_be16 dst)
{
struct tcp_header *th = packet->l4;
packet_set_port(&th->tcp_src, src, &th->tcp_csum);
packet_set_port(&th->tcp_dst, dst, &th->tcp_csum);
}
/* Sets the UDP source and destination port ('src' and 'dst' respectively) of
* the UDP header contained in 'packet'. 'packet' must be a valid UDP packet
* with its l4 marker properly populated. */
void
packet_set_udp_port(struct ofpbuf *packet, ovs_be16 src, ovs_be16 dst)
{
struct udp_header *uh = packet->l4;
if (uh->udp_csum) {
packet_set_port(&uh->udp_src, src, &uh->udp_csum);
packet_set_port(&uh->udp_dst, dst, &uh->udp_csum);
if (!uh->udp_csum) {
uh->udp_csum = htons(0xffff);
}
} else {
uh->udp_src = src;
uh->udp_dst = dst;
}
}