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sd-dhcp-client: improve BPF

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Try a bit harder to make the kernel drop packets not for us. This should reduce
the number of wakeups from n^2 to n in the number of dhcp clients, which admittedly
only makes a differenc in very extreme cases.
This commit is contained in:
Tom Gundersen 2014-04-06 19:23:33 +02:00
parent 0c79c68d93
commit 7429b07f82
4 changed files with 23 additions and 6 deletions
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2
src/libsystemd-network/dhcp-internal.h
View File

@ -29,7 +29,7 @@
#include "dhcp-protocol.h"
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link);
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t xid);
int dhcp_network_bind_udp_socket(int index, be32_t address, uint16_t port);
int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
const void *packet, size_t len);

21
src/libsystemd-network/dhcp-network.c
View File

@ -23,6 +23,7 @@
#include <string.h>
#include <linux/if_packet.h>
#include <net/ethernet.h>
#include <net/if_arp.h>
#include <stdio.h>
#include <unistd.h>
#include <linux/filter.h>
@ -31,18 +32,34 @@
#include "dhcp-internal.h"
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link)
{
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t xid) {
struct sock_filter filter[] = {
BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0), /* A <- packet length */
BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0), /* packet >= DHCPPacket ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
/* TODO: match ip.version */
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0), /* IP protocol == UDP ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)), /* A <- UDP destination port */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_PORT_CLIENT, 1, 0), /* UDP destination port == DHCP client port ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)), /* A <- DHCP op */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0), /* op == BOOTREPLY ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)), /* A <- DHCP header type */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0), /* header type == ARPHRD_ETHER ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)), /* A <- mac address length */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHER_ADDR_LEN, 1, 0), /* address length == ETHER_ADDR_LEN ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)), /* A <- client identifier */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0), /* client identifier == xid ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
/* TODO: match chaddr */
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)), /* A <- DHCP magic cookie */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0), /* cookie == DHCP magic cookie ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_RET + BPF_K, 65535), /* return all */
};
struct sock_fprog fprog = {

4
src/libsystemd-network/sd-dhcp-client.c
View File

@ -593,7 +593,7 @@ static int client_start(sd_dhcp_client *client) {
client->xid = random_u32();
r = dhcp_network_bind_raw_socket(client->index, &client->link);
r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid);
if (r < 0) {
client_stop(client, r);
@ -636,7 +636,7 @@ static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata)
client->state = DHCP_STATE_REBINDING;
client->attempt = 1;
r = dhcp_network_bind_raw_socket(client->index, &client->link);
r = dhcp_network_bind_raw_socket(client->index, &client->link, client->xid);
if (r < 0) {
client_stop(client, r);
return 0;

2
src/libsystemd-network/test-dhcp-client.c
View File

@ -190,7 +190,7 @@ int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
return 575;
}
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link)
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link, uint32_t id)
{
if (socketpair(AF_UNIX, SOCK_STREAM, 0, test_fd) < 0)
return -errno;