[FS#276] libpcap 1.7.4: netfilter compile check will not succeed; PCAP_SUPPORT_NETFILTER will never set

[LEDE Bugs]

The following task has a new comment added:

FS#276 - libpcap 1.7.4:  netfilter compile check will not succeed; PCAP_SUPPORT_NETFILTER will never set 
User who did this - InkblotAdmirer (InkblotAdmirer)

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The makefile includes this section:

  CONFIGURE_VARS += \
	ac_cv_linux_vers=$(LINUX_VERSION) \
	ac_cv_header_libusb_1_0_libusb_h=no \
	ac_cv_netfilter_can_compile=no

This appears to force a fail on the flag as hinted in the previous comment.  I changed it to:

  CONFIGURE_VARS += \
	ac_cv_linux_vers=$(LINUX_VERSION) \
	ac_cv_header_libusb_1_0_libusb_h=no

and the test now passes (with all LEDE patches and without my additional patch).  I'm not sure why it's forced to no, or how to go about toggling it to yes if something like iptables-mod-nflog is selected.

As to libpcap 1.8.1 (and the newer tcpdump) -- I've eyeballed these and it looks like they should be easy-ish to update with the exception of the first libpcap shared debian library patch.  I don't know what that patch is trying to accomplish and a non-trivial amount of work needs to be done to fix that patch given differences in objects.  Is there a compelling reason to upgrade?

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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=276#comment810