On Tue, Jun 24, 2014 at 12:58 PM, Michal Sekletar <[email protected]> wrote:
> On Thu, Jun 19, 2014 at 12:02:39PM -0500, Dan Williams wrote:
>> On Thu, 2014-06-19 at 18:59 +0200, Michal Sekletar wrote:
>> > Check that received DHCP packets actually include our MAC address in
>> > chaddr field. BPF interpreter has 32 bit wide registers but MAC address
>> > is 48 bits long so we have to do check in two steps.
>>
>> And if the MAC address is not 48 bits (Infiniband) or the interface type
>> doesn't really have a MAC address (PPP/PPPoE)? DHCP can be used in both
>> cases... If anything, the code that uses the MAC address should be
>> if-ed so it only executes when a MAC address is provided.
>
> I reconsidered. In filter code I can very easily find out type of device to
> which
> filter is attached and skip ethernet specific bits or fallback to something
> else. However filter already assumes ethernet data-link type moreover there
> is a ton of
> code in networkd which does likewise.
>
> I think we should merge patch as is right now. If somebody will hack up
> patches
> for supporting various data-link types I will be happy to patch filter
> accordingly.
Ok. I'm fine with that. Please push.
Just to make clear: I'd be happy if anyone wanted to turn all our libs
to work also on non-ethernet (and test it!), and would merge such
patches.
Cheers,
Tom
>> > src/libsystemd-network/dhcp-internal.h | 3 ++-
>> > src/libsystemd-network/dhcp-network.c | 15 +++++++++++++--
>> > src/libsystemd-network/sd-dhcp-client.c | 4 ++--
>> > src/libsystemd-network/test-dhcp-client.c | 2 +-
>> > 4 files changed, 18 insertions(+), 6 deletions(-)
>> >
>> > diff --git a/src/libsystemd-network/dhcp-internal.h
>> > b/src/libsystemd-network/dhcp-internal.h
>> > index 03cc824..fd86a70 100644
>> > --- a/src/libsystemd-network/dhcp-internal.h
>> > +++ b/src/libsystemd-network/dhcp-internal.h
>> > @@ -24,12 +24,13 @@
>> >
>> > #include <stdint.h>
>> > #include <linux/if_packet.h>
>> > +#include <net/ethernet.h>
>> >
>> > #include "socket-util.h"
>> >
>> > #include "dhcp-protocol.h"
>> >
>> > -int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
>> > uint32_t xid);
>> > +int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
>> > uint32_t xid, struct ether_addr mac_addr);
>> > int dhcp_network_bind_udp_socket(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);
>> > diff --git a/src/libsystemd-network/dhcp-network.c
>> > b/src/libsystemd-network/dhcp-network.c
>> > index d7ba0ef..e5fd6a8 100644
>> > --- a/src/libsystemd-network/dhcp-network.c
>> > +++ b/src/libsystemd-network/dhcp-network.c
>> > @@ -33,7 +33,7 @@
>> > #include "dhcp-internal.h"
>> >
>> > int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
>> > - uint32_t xid) {
>> > + uint32_t xid, struct ether_addr
>> > mac_addr) {
>> > 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 ? */
>> > @@ -56,7 +56,18 @@ int dhcp_network_bind_raw_socket(int index, union
>> > sockaddr_union *link,
>> > 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_IMM, htobe32(*((unsigned int *)
>> > &mac_addr))), /* A <- 4 bytes of client's MAC */
>> > + BPF_STMT(BPF_MISC + BPF_TAX, 0),
>> > /* X <- A */
>> > + BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket,
>> > dhcp.chaddr)), /* A <- 4 bytes of MAC from dhcp.chaddr */
>> > + BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),
>> > /* A xor X */
>> > + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),
>> > /* A == 0 ? */
>> > + BPF_STMT(BPF_RET + BPF_K, 0),
>> > /* ignore */
>> > + BPF_STMT(BPF_LD + BPF_IMM, htobe16(*((unsigned short *)
>> > (((char *) &mac_addr) + 4)))), /* A <- remainder of client's MAC */
>> > + BPF_STMT(BPF_MISC + BPF_TAX, 0),
>> > /* X <- A */
>> > + BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket,
>> > dhcp.chaddr) + 4), /* A <- remainder of MAC from dhcp.chaddr */
>> > + BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),
>> > /* A xor X */
>> > + BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),
>> > /* A == 0 ? */
>> > + BPF_STMT(BPF_RET + BPF_K, 0),
>> > /* ignore */
>> > 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 */
>> > diff --git a/src/libsystemd-network/sd-dhcp-client.c
>> > b/src/libsystemd-network/sd-dhcp-client.c
>> > index c1af6df..d44cad2 100644
>> > --- a/src/libsystemd-network/sd-dhcp-client.c
>> > +++ b/src/libsystemd-network/sd-dhcp-client.c
>> > @@ -719,7 +719,7 @@ static int client_start(sd_dhcp_client *client) {
>> >
>> > client->xid = random_u32();
>> >
>> > - r = dhcp_network_bind_raw_socket(client->index, &client->link,
>> > client->xid);
>> > + r = dhcp_network_bind_raw_socket(client->index, &client->link,
>> > client->xid, client->client_id.mac_addr);
>> > if (r < 0) {
>> > client_stop(client, r);
>> > return r;
>> > @@ -761,7 +761,7 @@ 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,
>> > client->xid);
>> > + r = dhcp_network_bind_raw_socket(client->index, &client->link,
>> > client->xid, client->client_id.mac_addr);
>> > if (r < 0) {
>> > client_stop(client, r);
>> > return 0;
>> > diff --git a/src/libsystemd-network/test-dhcp-client.c
>> > b/src/libsystemd-network/test-dhcp-client.c
>> > index 450b6d4..7cbe10d 100644
>> > --- a/src/libsystemd-network/test-dhcp-client.c
>> > +++ b/src/libsystemd-network/test-dhcp-client.c
>> > @@ -196,7 +196,7 @@ 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,
>> > uint32_t id)
>> > +int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
>> > uint32_t id, struct ether_addr mac)
>> > {
>> > if (socketpair(AF_UNIX, SOCK_STREAM, 0, test_fd) < 0)
>> > return -errno;
>>
>>
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