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Fix cmsg(3) API usage on OpenBSD

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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.
This commit is contained in:
Jérémie Courrèges-Anglas
2019-03-22 10:56:13 +01:00
committed by Simon Kelley
parent 1da81f7e23
commit c6cc455dd1
1 changed files with 6 additions and 3 deletions
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9
src/forward.c
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@@ -65,13 +65,15 @@ int send_from(int fd, int nowild, char *packet, size_t len,
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 *packet, size_t len,
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;
}