Lookup interface index when IN_PKTINFO isn't available (#27692)
Lookup interface index when IN_PKTINFO isn't available (#27692)

* Lookup interface index when IN_PKTINFOY
 isn't available

* Address comments

ericstj/corefx,Jiayili1/corefx,wtgodbe/corefx,ViktorHofer/corefx,wtgodbe/corefx,wtgodbe/corefx,ptoonen/corefx,BrennanConroy/corefx,ViktorHofer/corefx,ericstj/corefx,ViktorHofer/corefx,Jiayili1/corefx,mmitche/corefx,ViktorHofer/corefx,ptoonen/corefx,wtgodbe/corefx,ViktorHofer/corefx,ViktorHofer/corefx,ViktorHofer/corefx,Jiayili1/corefx,Jiayili1/corefx,wtgodbe/corefx,wtgodbe/corefx,shimingsg/corefx,mmitche/corefx,mmitche/corefx,ericstj/corefx,ptoonen/corefx,shimingsg/corefx,mmitche/corefx,shimingsg/corefx,Jiayili1/corefx,Jiayili1/corefx,Jiayili1/corefx,ericstj/corefx,mmitche/corefx,ptoonen/corefx,ptoonen/corefx,ptoonen/corefx,ptoonen/corefx,ericstj/corefx,shimingsg/corefx,mmitche/corefx,wtgodbe/corefx,ericstj/corefx,shimingsg/corefx,shimingsg/corefx,ericstj/corefx,BrennanConroy/corefx,BrennanConroy/corefx,mmitche/corefx,shimingsg/corefx