There are three reasons for me to add this support:
1.When no interface is specified in an IPV6_PKTINFO ancillary data
item, the interface specified in an IPV6_PKTINFO sticky optionis
is used.
RFC3542:
6.7. Summary of Outgoing Interface Selection
This document and [RFC-3493] specify various methods that affect the
selection of the packet's outgoing interface. This subsection
summarizes the ordering among those in order to ensure deterministic
behavior.
For a given outgoing packet on a given socket, the outgoing interface
is determined in the following order:
1. if an interface is specified in an IPV6_PKTINFO ancillary data
item, the interface is used.
2. otherwise, if an interface is specified in an IPV6_PKTINFO sticky
option, the interface is used.
2.When no IPV6_PKTINFO ancillary data is received,getsockopt() should
return the sticky option value which set with setsockopt().
RFC 3542:
Issuing getsockopt() for the above options will return the sticky
option value i.e., the value set with setsockopt(). If no sticky
option value has been set getsockopt() will return the following
values:
3.Make the setsockopt implementation POSIX compliant.
Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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