IP_BINDANY(SYN_SENT ): return packets not accepted by kernel

star hegui_you at 126.com
Thu Oct 25 01:39:18 UTC 2018


Hello all, 

I am testing IP_BINDANY functionality with a small C program. I can 
bind to a foreign (non existing) address, and syn packets are being 
sent with the bound source IP address and port. Return (ACK) packets 
are reaching the host (I can see the SYN-ACK packet in tcpdump), but 
the third packet in TCP handshake is not getting generated. It looks 
like the second SYN-ACK is not getting accepted by the kernel. 

<http://freebsd.1045724.x6.nabble.com/file/t354462/TIM%E5%9B%BE%E7%89%8720181024175304.png> 


My ipfw:
root at bsd:~ # ipfw list
00100 fwd 127.0.0.1,3128 tcp from any to any 80 in recv igb1
00300 fwd 127.0.0.1 ip from any  to any uid 0  in recv igb0
65534 allow ip from any to any
65535 deny ip from any to any


Refer to other pages: 
http://freebsd.1045724.x6.nabble.com/IP-BINDANY-return-packets-not-accepted-by-kernel-td4017905.html

but not work!

can anybody help me? Thanks





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