subnet.data

# Compiled by Clang
# Check that the ipv4_dst is in 192.168.1.0/24
-- c
#include <stdint.h>

#define NETMASK 0xffffff00
#define SUBNET 0xc0a80100

struct eth_hdr {
    uint8_t eth_src[6];
    uint8_t eth_dst[6];
    uint16_t eth_type;
};

struct vlan_hdr {
    uint16_t vlan;
    uint16_t eth_type;
};

struct ipv4_hdr {
    uint8_t ver_ihl;
    uint8_t tos;
    uint16_t total_length;
    uint16_t id;
    uint16_t frag;
    uint8_t ttl;
    uint8_t proto;
    uint16_t csum;
    uint32_t src;
    uint32_t dst;
};

uint64_t entry(void *mem)
{
    struct eth_hdr *eth_hdr = (void *)mem;
    uint16_t eth_type;
    void *next = eth_hdr;

    if (eth_hdr->eth_type == __builtin_bswap16(0x8100)) {
        struct vlan_hdr *vlan_hdr = (void *)(eth_hdr + 1);
        eth_type = vlan_hdr->eth_type;
        next = vlan_hdr + 1;
    } else {
        eth_type = eth_hdr->eth_type;
        next = eth_hdr + 1;
    }

    if (eth_type == __builtin_bswap16(0x0800)) {
        struct ipv4_hdr *ipv4_hdr = next;
        if ((ipv4_hdr->dst & __builtin_bswap32(NETMASK)) == __builtin_bswap32(SUBNET)) {
            return 1;
        }
    }

    return 0;
}
-- asm
mov r2, 0xe
ldxh r3, [r1+12]
jne r3, 0x81, +2
mov r2, 0x12
ldxh r3, [r1+16]
and r3, 0xffff
jne r3, 0x8, +5
add r1, r2
mov r0, 0x1
ldxw r1, [r1+16]
and r1, 0xffffff
jeq r1, 0x1a8c0, +1
mov r0, 0x0
exit
-- mem
00 00 c0 9f a0 97 00 a0 
cc 3b bf fa 08 00 45 10 
00 3c 46 3c 40 00 40 06 
73 1c c0 a8 01 02 c0 a8 
01 01 06 0e 00 17 99 c5 
a0 ec 00 00 00 00 a0 02 
7d 78 e0 a3 00 00 02 04 
05 b4 04 02 08 0a 00 9c 
27 24 00 00 00 00 01 03 
03 00 
-- result
0x1