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Explain initialization when using csum()

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The checksum method csum() requires its output location to be
intialized to zero when that output location is part of the
checksum.  Add comments to the various places where csum is
called documenting where the initialization has occurred.

Signed-off-by: Ryan Moats <rmoats@us.ibm.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
This commit is contained in:
Ryan Moats
2016-07-24 18:36:35 +00:00
committed by Ben Pfaff
parent 218f9539f9
commit ece9c2947d
4 changed files with 6 additions and 0 deletions
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3
lib/flow.c
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@@ -2226,6 +2226,7 @@ flow_compose_l4(struct dp_packet *p, const struct flow *flow)
icmp = dp_packet_put_zeros(p, l4_len);
icmp->icmp_type = ntohs(flow->tp_src);
icmp->icmp_code = ntohs(flow->tp_dst);
/* Checksum has already been zeroed by put_zeros call. */
icmp->icmp_csum = csum(icmp, ICMP_HEADER_LEN);
} else if (flow->nw_proto == IPPROTO_IGMP) {
struct igmp_header *igmp;
@@ -2235,6 +2236,7 @@ flow_compose_l4(struct dp_packet *p, const struct flow *flow)
igmp->igmp_type = ntohs(flow->tp_src);
igmp->igmp_code = ntohs(flow->tp_dst);
put_16aligned_be32(&igmp->group, flow->igmp_group_ip4);
/* Checksum has already been zeroed by put_zeros call. */
igmp->igmp_csum = csum(igmp, IGMP_HEADER_LEN);
} else if (flow->nw_proto == IPPROTO_ICMPV6) {
struct icmp6_hdr *icmp;
@@ -2323,6 +2325,7 @@ flow_compose(struct dp_packet *p, const struct flow *flow)
ip = dp_packet_l3(p);
ip->ip_tot_len = htons(p->l4_ofs - p->l3_ofs + l4_len);
/* Checksum has already been zeroed by put_zeros call. */
ip->ip_csum = csum(ip, sizeof *ip);
} else if (flow->dl_type == htons(ETH_TYPE_IPV6)) {
struct ovs_16aligned_ip6_hdr *nh;