IP_RECVTTL socket option.

[Matthew N. Dodd]

I've committed the IP_RECVTTL socket option to FreeBSD.

(From ip(4))
%%%
If the IP_RECVTTL option is enabled on a SOCK_DGRAM socket, the
recvmsg(2) call will return the IP TTL (time to live) field for a UDP
datagram. The msg_control field in the msghdr structure points to a
buffer that contains a cmsghdr structure followed by the TTL. The cms-
ghdr fields have the following values:

cmsg_len = sizeof(u_char)
cmsg_level = IPPROTO_IP
cmsg_type = IP_RECVTTL
%%%

This is needed for things like:

http://files.multicastdns.org/draft-cheshire-dnsext-multicastdns.txt

It would be useful of NetBSD and OpenBSD provided this feature as well.

[itojun-MMLKt5r8Ll2sTnJN9+]

Post by Matthew N. Dodd
I've committed the IP_RECVTTL socket option to FreeBSD.
(From ip(4))
%%%
If the IP_RECVTTL option is enabled on a SOCK_DGRAM socket, the
recvmsg(2) call will return the IP TTL (time to live) field for a UDP
datagram. The msg_control field in the msghdr structure points to a
buffer that contains a cmsghdr structure followed by the TTL. The cms-
cmsg_len = sizeof(u_char)
cmsg_level = IPPROTO_IP
cmsg_type = IP_RECVTTL
%%%
http://files.multicastdns.org/draft-cheshire-dnsext-multicastdns.txt
It would be useful of NetBSD and OpenBSD provided this feature as well.

FYI, IPv6 counterpart (IPV6_{RECV,}HOPLIMIT in 2292bis API) uses
cmsg_len = sizeof(int). not sure why it is not u_int8_t.

any reason why you don't support it for SOCK_RAW?

itojun

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