Hi.
I found a problem in man7/ip.7 in man-pages-3.32.tar.bz2.
(I also checked man-pages git repository and the text is not changed.)
ip(7) describes that the argument for IP_MULTICAST_IF is ip_mreqn or ip_mreq:
IP_MULTICAST_IF
Set the local device for a multicast socket. Argument is an
ip_mreqn or ip_mreq structure similar to IP_ADD_MEMBERSHIP.
But it should be ip_mreqn or in_addr.
It is different from IP_ADD_MEMBERSHIP.
do_ip_setsockopt() in linux-2.6.37/net/ipv4/ip_sockglue.c supports
struct ip_mreqn and struct in_addr.
| case IP_MULTICAST_IF:
| {
| struct ip_mreqn mreq;
| struct net_device *dev = NULL;
|
| if (sk->sk_type == SOCK_STREAM)
| goto e_inval;
| /*
| * Check the arguments are allowable
| */
|
| if (optlen < sizeof(struct in_addr))
| goto e_inval;
|
| err = -EFAULT;
| if (optlen >= sizeof(struct ip_mreqn)) {
| if (copy_from_user(&mreq, optval, sizeof(mreq)))
| break;
| } else {
| memset(&mreq, 0, sizeof(mreq));
| if (optlen >= sizeof(struct in_addr) &&
| copy_from_user(&mreq.imr_address, optval,
| sizeof(struct in_addr)))
| break;
| }
The third argument of copy_from_user() is sizeof(mreq) and
sizeof(struct in_addr).
The former is sizeof(struct mreqn) because the type of mreq is struct mreqn.
The code copies struct mreqn or struct in_addr from user space.
So, I think Linux supports struct mreqn and struct in_addr for IP_MULTICAST_IF.
At the original API of BSD multicast, IP_MULTICAST_IF takes struct in_addr.
http://www.kohala.com/start/mcast.api.txt :
struct in_addr addr;
setsockopt(sock, IPPROTO_IP, IP_MULTICAST_IF, &addr, sizeof(addr))
Note that I also reported this problem to
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=607979
--
Tanaka Akira
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