question related to /sbin/ipfw/ipfw2.c

[Ganbold]

Hi,

What does following part of src/sbin/ipfw/ipfw2.c code?
...
static void
fill_ip(ipfw_insn_ip *cmd, char *av)
{
    int len = 0;
    uint32_t *d = ((ipfw_insn_u32 *)cmd)->d;

    cmd->o.len &= ~F_LEN_MASK;    /* zero len */
-----------------------------------
    if (strncmp(av, "table(", 6) == 0) {
        char *p = strchr(av + 6, ',');

        if (p)
            *p++ = '\0';
        cmd->o.opcode = O_IP_DST_LOOKUP;
        cmd->o.arg1 = strtoul(av + 6, NULL, 0);
        if (p) {
            cmd->o.len |= F_INSN_SIZE(ipfw_insn_u32);
            d[0] = strtoul(p, NULL, 0);
        } else
            cmd->o.len |= F_INSN_SIZE(ipfw_insn);
        return;
    }
-----------------------------------

Specially, what does following code?
...
        cmd->o.opcode = O_IP_DST_LOOKUP;
        cmd->o.arg1 = strtoul(av + 6, NULL, 0);
        if (p) {
            cmd->o.len |= F_INSN_SIZE(ipfw_insn_u32);
            d[0] = strtoul(p, NULL, 0);
        } else
            cmd->o.len |= F_INSN_SIZE(ipfw_insn);
...

thanks,

Ganbold

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hunchbacks.