I am running into an issue where tcpreplay fails with the error "Fatal Error: failed to open device en0: Unable to open /dev/bpfX: Resource busy" when trying to replay a pcap file through my wifi interface (en0)

Looking at https://github.com/appneta/tcpreplay/blob/master/src/common/sendpacket.c#L1056

the maximum bpf device files tried is 10 which is hardcoded as a magic number. Increasing this by doing something like #define BPFDEV_LIMIT 10 and replacing the loop condition and array declaration seems to resolve the issue. An even better approach may be to parameterize that value by defining a new flag.

I am running MacOS Mojave 10.14.1 on a Macbook Pro 15" 2016

The brew installed version of tcpreplay has the same issue.