In article <47BC4505.9020105@xxxxxxxxxxxx> (at Wed, 20 Feb 2008 10:19:33 -0500), Chinh Nguyen <cnguyen@xxxxxxxxxxxx> says: > Theoretically, I can specify the source address of the outgoing packet > on an IPv6 socket by using sendmsg with IPV6_PKTINFO option enabled and > in6_pktinfo. However, I cannot do this when the source address I specify > is IPv4-mapped. The system still chooses the IPv4 source based on the > routing table. Does linux IPv6 support IPv4-mapped addresses for > sendmsg? Note I do not have trouble with the destination IPv4-mapped > address in the destination sockaddr_in6 structure. Sendmsg itself, yes, but IPV6_PKTINFO, no. Semantics of ipv4-mapped address (in basic API) in that socket option (in advanced API) is undefined. > If I have enabled IPV6_PKTINFO on an IPv6 socket, I would expect to > receive both IPv6 and IPv4 local address (as IPv4-mapped address) info > in an in6_pktinfo when using recvmsg. But I only receive data for IPv6 > packets. To receive IPv4 local address info from an IPv4 incoming > packet, I have to also enable IP_PKTINFO on the IPv6 socket. > Furthermore, the data will be a regular IPv4 address in an in_pktinfo > structure. If you need "advanced" things, go native way. And, well, I'd even strongly suggest not to use IPv4-mapped addresses unless you have very very good reason. --yoshfuji - To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
