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ipmr: Add high byte of VIF ID to igmpmsg

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Use the unused3 byte in struct igmpmsg to hold the high 8 bits of the
VIF ID.

If using more than 255 IPv4 multicast interfaces it is necessary to have
access to a VIF ID for cache reports that is wider than 8 bits, the VIF
ID present in the igmpmsg reports sent to mroute_sk was only 8 bits wide
in the igmpmsg header.  Adding the high 8 bits of the 16 bit VIF ID in
the unused byte allows use of more than 255 IPv4 multicast interfaces.

Signed-off-by: Paul Davey <paul.davey@alliedtelesis.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paul Davey 2020-09-08 10:04:07 +12:00 • committed by David S. Miller
parent 501cb00890
commit c8715a8e9f
2 changed files with 8 additions and 4 deletions
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4
include/uapi/linux/mroute.h
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@ -113,8 +113,8 @@ struct igmpmsg {
__u32 unused1,unused2;
unsigned char im_msgtype; /* What is this */
unsigned char im_mbz; /* Must be zero */
unsigned char im_vif; /* Interface (this ought to be a vifi_t!) */
unsigned char unused3;
unsigned char im_vif; /* Low 8 bits of Interface */
unsigned char im_vif_hi; /* High 8 bits of Interface */
struct in_addr im_src,im_dst;
};