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sd-dhcp-client: eagerly drop too small packets

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If they are too small to fit the IP+UDP+DHCP headers they can be of no use, so
don't waste resources parsing them. This is at the cost of losing some verbosity
in the logging.
This commit is contained in:
Tom Gundersen
2014-04-06 19:42:11 +02:00
parent 3b7ca119fd
commit 0c79c68d93
3 changed files with 12 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/libsystemd-network/dhcp-network.c
+5 -2
View File
@@ -34,11 +34,14 @@
int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link)
{
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 */
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_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? */
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_RET + BPF_K, 65535), /* return all */
};
src/libsystemd-network/dhcp-packet.c
-14
View File
@@ -113,13 +113,6 @@ int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
/* IP */
if (len < DHCP_IP_SIZE) {
log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "
" smaller than IP header (%u bytes)", len,
DHCP_IP_SIZE);
return -EINVAL;
}
if (packet->ip.version != IPVERSION) {
log_dhcp_client(client, "ignoring packet: not IPv4");
return -EINVAL;
@@ -152,13 +145,6 @@ int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
return -EINVAL;
}
if (len < DHCP_IP_UDP_SIZE) {
log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "
" smaller than IP+UDP header (%u bytes)", len,
DHCP_IP_UDP_SIZE);
return -EINVAL;
}
if (len < hdrlen + be16toh(packet->udp.len)) {
log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "
"smaller than expected (%zu) by UDP header", len,
src/libsystemd-network/sd-dhcp-client.c
+7 -8
View File
@@ -931,12 +931,6 @@ static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message,
assert(client->event);
assert(message);
if (len < DHCP_MESSAGE_SIZE) {
log_dhcp_client(client, "message too small (%d bytes): "
"ignoring", len);
return 0;
}
if (be32toh(message->magic) != DHCP_MAGIC_COOKIE) {
log_dhcp_client(client, "not a DHCP message: ignoring");
return 0;
@@ -1081,7 +1075,11 @@ static int client_receive_message_udp(sd_event_source *s, int fd,
return -ENOMEM;
len = read(fd, message, buflen);
if (len < 0)
if (len < 0) {
log_dhcp_client(client, "could not receive message from UDP "
"socket: %s", strerror(errno));
return 0;
} else if ((size_t)len < sizeof(DHCPMessage))
return 0;
return client_handle_message(client, message, len);
@@ -1122,7 +1120,8 @@ static int client_receive_message_raw(sd_event_source *s, int fd,
log_dhcp_client(client, "could not receive message from raw "
"socket: %s", strerror(errno));
return 0;
}
} else if ((size_t)len < sizeof(DHCPPacket))
return 0;
for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (cmsg->cmsg_level == SOL_PACKET && cmsg->cmsg_type == PACKET_AUXDATA) {