+ 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;
+}
+
+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;
+ }