You need a typemap for "u_char *" (just the one "*") and use "u_char * &buf" as the declaration for the argument.

This is from fuzzy memory so let me know if that worked.

I made the changes as you suggested. My XS file now reads:

int
libnet_init_packet(p_size, buf)
        size_t p_size
        u_char * & buf
    OUTPUT:
        buf
[download]

I also did the same thing for libnet_destory_packet(). It now compiles as I hoped it would, but I get a memory fault when I run this test script:

# Before `make install' is performed this script should be runnable wi
+th
# `make test'. After `make install' it should work as `perl test.pl'

######################### We start with some black magic to print on f
+ailure.

# Change 1..1 below to 1..last_test_to_print .
# (It may become useful if the test is moved to ./t subdirectory.)

BEGIN { $| = 1; print "1..1\n"; }
END {print "not ok 1\n" unless $loaded;}
use Net::LibnetRaw;
$loaded = 1;
print "ok 1\n";

my $buf;
Net::LibnetRaw::libnet_init_packet(IP_H, $buf);
my $dip = Net::LibnetRaw::libnet_name_resolve("10.0.0.4", 1);
my $sip = Net::LibnetRaw::libnet_name_resolve("10.0.0.1", 1);
#my $sock = Net::LibnetRaw::libnet_open_raw_sock(IPPROTO_RAW);
Net::LibnetRaw::libnet_build_ip(ICMP_ECHO_H, 0, 12345, 0, 127, 0, $sip
+, $dip, undef, 0, $buf);
Net::LibnetRaw::libnet_write_ip($sock, $buf, IP_H + ICMP_ECHO_H);
Net::LibnetRaw::libnet_close_raw_sock($sock);
Net::LibnetRaw::libnet_destroy_packet($buf);

######################### End of black magic.

# Insert your test code below (better if it prints "ok 13"
# (correspondingly "not ok 13") depending on the success of chunk 13
# of the test code):
[download]

It appears that the error occurs when I call libnet_build_ip(). It seems pretty clear that there is an issue with the passage and management of buf. Buf is supposed to come back out by reference here. My XSUB for libnet_build_ip() is:

int
libnet_build_ip(len, tos, id, frag, ttl, prot, saddr, daddr, payload, 
+payload_s, buf)
                u_short len
                u_char tos
                u_short id
                u_short frag
                u_char ttl
                u_char prot
                u_long saddr
                u_long daddr
                const u_char * payload
                int payload_s
                u_char & buf
        OUTPUT:
                buf
[download]

It is appropriate for the function prototype. buf is not passed as a C "u_char **" like with libnet_init_packet(). buf should be holding a C pointer to the meory location allocated by libnet_packet_init(), which is basically a wrapper to malloc() which passed the buf back by reference.

My guess is that there is some issue related to storing a pointer to a memory location used in C in a perl reference. If my guess is correction, how do I work around this? If not, then what the hell am I doing wrong? I've considered writing additional C code to simply allow $buf to hold a number which would act sort of like a "buffer descriptor" ala UNIX file I/O and keep the pointers in perl, but I really want to do as much of this in perl as possible.

Your solutions are greatly appreciated.

Can you post the generated C code that relates to the processing of the problem argument (near the top and bottom of each generated subroutine)? You want the pointer to be stashed as an opaque value (usually an unsigned long integer, UV). If you have the typemap class wrong then the C code might be trying to copy the data in the allocated buffer rather than just stashing the pointer's value.

I don't recall which typemap class is meant to do this and looking at the generated C code prevents me from having to assembly the pieces myself and possible get confused in the process (I'm often easily confused).

        - tye (but my friends call me "Tye")