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From c6cc455dd191fbea56ee14a0ef88a7d655a6fe9a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=A9mie=20Courr=C3=A8ges-Anglas?= <jca@wxcvbn.org>
Date: Fri, 22 Mar 2019 10:56:13 +0100
Subject: [PATCH 48/57] 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.
Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
---
src/forward.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
--- a/src/forward.c
+++ b/src/forward.c
@@ -65,13 +65,15 @@ int send_from(int fd, int nowild, char *
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 @@ int send_from(int fd, int nowild, char *
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;
}
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