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Optimize the ARP BPF bytecode to use fewer instructions.

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This commit is contained in:
Nicholas J. Kain 2011-07-01 02:49:19 -04:00
parent 927e2590a2
commit 0e55bfd4fd
1 changed files with 10 additions and 18 deletions
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28
ndhc/arp.c
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@ -50,25 +50,17 @@ static int arp_packet_num;
static int arp_open_fd(struct client_state_t *cs)
{
static const struct sock_filter sf_arp[] = {
// Verify that the frame has ethernet protocol type of ARP.
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETH_P_ARP, 1, 0),
// Verify that the frame has ethernet protocol type of ARP
// and that the ARP hardware type field indicates Ethernet.
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, 12),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (ETH_P_ARP << 16) | ARPHRD_ETHER,
1, 0),
BPF_STMT(BPF_RET + BPF_K, 0),
// Verify that the ARP hardware type field indicates Ethernet.
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 14),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0),
BPF_STMT(BPF_RET + BPF_K, 0),
// Verify that the ARP protocol type field indicates IP.
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 16),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETH_P_IP, 1, 0),
BPF_STMT(BPF_RET + BPF_K, 0),
// Verify that the ARP hardware address length field is 6.
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 18),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 6, 1, 0),
BPF_STMT(BPF_RET + BPF_K, 0),
// Verify that the ARP protocol address length field is 4.
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 19),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 4, 1, 0),
// Verify that the ARP protocol type field indicates IP, the ARP
// hardware address length field is 6, and the ARP protocol address
// length field is 4.
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, 16),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (ETH_P_IP << 16) | 0x0604, 1, 0),
BPF_STMT(BPF_RET + BPF_K, 0),
// Sanity tests passed, so send all possible data.
BPF_STMT(BPF_RET + BPF_K, 0x0fffffff),