libpcap Binding & Cabal Question

Dominic Steinitz dominic.steinitz at
Fri Apr 14 03:57:05 EDT 2006

I am trying to build the binding for libpcap.

Unfortunately when I run hsc2hs I get errors.

[dom at tility pcap]$ hsc2hs Pcap.hs
Pcap.hs:121:21: net/bpf.h: No such file or directory
Pcap.hs: In function `main':
Pcap.hs:461: error: structure has no member named `sa_len'

The first one is easily fixed. The version of libpcap I downloaded from (LIBPCAP 0.9.4) contains pcap-bpf.h not net/bpf.h (so I 
replaced #inlcude <net/bpf.h> with #include <pcap-bpf.h>).

The second one is a result because in some systems socket addresses are 
fixed-length and sizeof (struct sockaddr) gives the size of the structure but 
in other systems the socket address is variable length and there's an sa_len 
field giving the length of the structure.

The libpcap authors handle this by using configure to see if the sa_len field 
exists. If it does then

#define SA_LEN(addr)    (get_sa_len(addr))

If does not then (actually it's more complicated than this but I don't want to 
clutter up an already cluttered email)

#define SA_LEN(addr)   (sizeof (struct sockaddr))

Finally to my questions. 

1. How do I get Cabal to check for the existence of sa_len? I'm guessing I 
follow the instructions in "2.2. System-dependent parameters" but I have 
never used autoconf in my life so if there were another easier way I'd be 
happy to hear about it.

2. How do I tell Cabal I need LIBPCAP 0.9.4?


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