Fix cmsg(3) API usage on OpenBSD
msg_controllen should be set using CMSG_SPACE() to account for padding.
RFC3542 provides more details:
While sending an application may or may not include padding at the end
of last ancillary data in msg_controllen and implementations must
accept both as valid.
At least OpenBSD rejects control messages if msg_controllen doesn't
account for padding, so use CMSG_SPACE() for maximal portability. This
is consistent with the example provided in the Linux cmsg(3) manpage.
diff --git a/src/forward.c b/src/forward.c
index 71ca45c..dd22a45 100644
--- a/src/forward.c
+++ b/src/forward.c
@@ -65,13 +65,15 @@
struct in_pktinfo p;
p.ipi_ifindex = 0;
p.ipi_spec_dst = source->addr4;
+ msg.msg_controllen = CMSG_SPACE(sizeof(struct in_pktinfo));
memcpy(CMSG_DATA(cmptr), &p, sizeof(p));
- msg.msg_controllen = cmptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
+ cmptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
cmptr->cmsg_level = IPPROTO_IP;
cmptr->cmsg_type = IP_PKTINFO;
#elif defined(IP_SENDSRCADDR)
+ msg.msg_controllen = CMSG_SPACE(sizeof(struct in_addr));
memcpy(CMSG_DATA(cmptr), &(source->addr4), sizeof(source->addr4));
- msg.msg_controllen = cmptr->cmsg_len = CMSG_LEN(sizeof(struct in_addr));
+ cmptr->cmsg_len = CMSG_LEN(sizeof(struct in_addr));
cmptr->cmsg_level = IPPROTO_IP;
cmptr->cmsg_type = IP_SENDSRCADDR;
#endif
@@ -81,8 +83,9 @@
struct in6_pktinfo p;
p.ipi6_ifindex = iface; /* Need iface for IPv6 to handle link-local addrs */
p.ipi6_addr = source->addr6;
+ msg.msg_controllen = CMSG_SPACE(sizeof(struct in6_pktinfo));
memcpy(CMSG_DATA(cmptr), &p, sizeof(p));
- msg.msg_controllen = cmptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
+ cmptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
cmptr->cmsg_type = daemon->v6pktinfo;
cmptr->cmsg_level = IPPROTO_IPV6;
}