libsystemd-network: Speed up checksum computation using 64 bit integers

[elogind.git] / src / libsystemd-network / dhcp-packet.c

diff --git a/src/libsystemd-network/dhcp-packet.c b/src/libsystemd-network/dhcp-packet.c
index bed942fd84345d0af51fa80dd3b9efe973408c16..fba9c46ef226fd9e3cf4d0bdbe2b67879c0e3aac 100644 (file)
--- a/src/libsystemd-network/dhcp-packet.c
+++ b/src/libsystemd-network/dhcp-packet.c
@@ -43,23 +43,13 @@ int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid,
 
         assert(op == BOOTREQUEST || op == BOOTREPLY);
 
-        *opt = (uint8_t *)(message + 1);
-
-        if (*optlen < 4)
-                return -ENOBUFS;
-        *optlen -= 4;
-
         message->op = op;
         message->htype = ARPHRD_ETHER;
         message->hlen = ETHER_ADDR_LEN;
         message->xid = htobe32(xid);
+        message->magic = htobe32(DHCP_MAGIC_COOKIE);
 
-        (*opt)[0] = 0x63;
-        (*opt)[1] = 0x82;
-        (*opt)[2] = 0x53;
-        (*opt)[3] = 0x63;
-
-        *opt += 4;
+        *opt = (uint8_t *)(message + 1);
 
         err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1,
                                  &type);
@@ -69,21 +59,48 @@ int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid,
         return 0;
 }
 
-uint16_t dhcp_packet_checksum(void *buf, int len) {
-        uint32_t sum;
-        uint16_t *check;
-        int i;
-        uint8_t *odd;
+uint16_t dhcp_packet_checksum(void *buf, size_t len) {
+        uint64_t *buf_64 = buf;
+        uint64_t *end_64 = (uint64_t*)buf + (len / sizeof(uint64_t));
+        uint32_t *buf_32;
+        uint16_t *buf_16;
+        uint8_t *buf_8;
+        uint64_t sum = 0;
 
-        sum = 0;
-        check = buf;
+        while (buf_64 < end_64) {
+                sum += *buf_64;
+                if (sum < *buf_64)
+                        sum++;
 
-        for (i = 0; i < len / 2 ; i++)
-                sum += check[i];
+                buf_64 ++;
+        }
 
-        if (len & 0x01) {
-                odd = buf;
-                sum += odd[len - 1];
+        buf_32 = (uint32_t*)buf_64;
+
+        if (len & sizeof(uint32_t)) {
+                sum += *buf_32;
+                if (sum < *buf_32)
+                        sum++;
+
+                buf_32 ++;
+        }
+
+        buf_16 = (uint16_t*)buf_32;
+
+        if (len & sizeof(uint16_t)) {
+                sum += *buf_16;
+                if (sum < *buf_16)
+                        sum ++;
+
+                buf_16 ++;
+        }
+
+        buf_8 = (uint8_t*)buf_16;
+
+        if (len & sizeof(uint8_t)) {
+                sum += *buf_8;
+                if (sum < *buf_8)
+                        sum++;
         }
 
         while (sum >> 16)
@@ -123,10 +140,8 @@ 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);
+        if (packet->ip.version != IPVERSION) {
+                log_dhcp_client(client, "ignoring packet: not IPv4");
                 return -EINVAL;
         }
 
@@ -150,17 +165,10 @@ int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
                 return -EINVAL;
         }
 
-        if (dhcp_packet_checksum(&packet->ip, hdrlen)) {
-                log_dhcp_client(client, "ignoring packet: invalid IP checksum");
-                return -EINVAL;
-        }
-
         /* UDP */
 
-        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);
+        if (packet->ip.protocol != IPPROTO_UDP) {
+                log_dhcp_client(client, "ignoring packet: not UDP");
                 return -EINVAL;
         }
 
@@ -171,6 +179,22 @@ int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
                 return -EINVAL;
         }
 
+        if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {
+                log_dhcp_client(client, "ignoring packet: to port %u, which "
+                                "is not the DHCP client port (%u)",
+                                be16toh(packet->udp.dest), DHCP_PORT_CLIENT);
+                return -EINVAL;
+        }
+
+        /* checksums - computing these is relatively expensive, so only do it
+           if all the other checks have passed
+         */
+
+        if (dhcp_packet_checksum(&packet->ip, hdrlen)) {
+                log_dhcp_client(client, "ignoring packet: invalid IP checksum");
+                return -EINVAL;
+        }
+
         if (checksum && packet->udp.check) {
                 packet->ip.check = packet->udp.len;
                 packet->ip.ttl = 0;
@@ -182,12 +206,5 @@ int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
                 }
         }
 
-        if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {
-                log_dhcp_client(client, "ignoring packet: to port %u, which "
-                                "is not the DHCP client port (%u)",
-                                be16toh(packet->udp.dest), DHCP_PORT_CLIENT);
-                return -EINVAL;
-        }
-
         return 0;
 }