packet: Add IP pseudoheader checksum calculation.

As OVS adds userspace support for being the endpoint in protocols
like tunnels, it will need to be able to calculate pseudoheaders
as part of the checksum calculation.

Signed-off-by: Jesse Gross <jesse@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>

lib/packets.c

@@ -1043,3 +1043,17 @@ compose_arp(struct dp_packet *b, const uint8_t eth_src[ETH_ADDR_LEN],
     dp_packet_set_frame(b, eth);
     dp_packet_set_l3(b, arp);
 }
+
+uint32_t
+packet_csum_pseudoheader(const struct ip_header *ip)
+{
+    uint32_t partial = 0;
+
+    partial = csum_add32(partial, get_16aligned_be32(&ip->ip_src));
+    partial = csum_add32(partial, get_16aligned_be32(&ip->ip_dst));
+    partial = csum_add16(partial, htons(ip->ip_proto));
+    partial = csum_add16(partial, htons(ntohs(ip->ip_tot_len) -
+                                        IP_IHL(ip->ip_ihl_ver) * 4));
+
+    return partial;
+}

lib/packets.h

@@ -806,5 +806,6 @@ void packet_format_tcp_flags(struct ds *, uint16_t);
 const char *packet_tcp_flag_to_string(uint32_t flag);
 void compose_arp(struct dp_packet *b, const uint8_t eth_src[ETH_ADDR_LEN],
                  ovs_be32 ip_src, ovs_be32 ip_dst);
+uint32_t packet_csum_pseudoheader(const struct ip_header *);
 
 #endif /* packets.h */

tests/library.at

@@ -7,7 +7,7 @@ AT_CHECK([ovstest test-flows flows pcap], [0], [checked 247 packets, 0 errors
 AT_CLEANUP
 
 AT_SETUP([test TCP/IP checksumming])
-AT_CHECK([ovstest test-csum], [0], [....#....#....###................................#................................#
+AT_CHECK([ovstest test-csum], [0], [....#....#....####................................#................................#
 ])
 AT_CLEANUP
 

tests/test-csum.c

@@ -20,11 +20,13 @@
 #include <assert.h>
 #include <inttypes.h>
 #include <netinet/in.h>
+#include <netinet/ip.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include "crc32c.h"
 #include "ovstest.h"
+#include "packets.h"
 #include "random.h"
 #include "unaligned.h"
 #include "util.h"
@@ -175,6 +177,34 @@ test_crc32c(void)
     mark('#');
 }
 
+/* Check the IP pseudoheader calculation. */
+static void
+test_pseudo(void)
+{
+    /* Try an IP header similar to one that the tunnel code
+     * might generate. */
+    struct ip_header ip = {
+        .ip_ihl_ver = IP_IHL_VER(5, 4),
+        .ip_tos = 0,
+        .ip_tot_len = htons(134),
+        .ip_id = 0,
+        .ip_frag_off = htons(IP_DF),
+        .ip_ttl = 64,
+        .ip_proto = IPPROTO_UDP,
+        .ip_csum = htons(0x1265),
+        .ip_src = { .hi = htons(0x1400), .lo = htons(0x0002) },
+        .ip_dst = { .hi = htons(0x1400), .lo = htons(0x0001) }
+    };
+
+    assert(packet_csum_pseudoheader(&ip) == 0x8628);
+
+    /* And also test something totally different to check for
+     * corner cases. */
+    memset(&ip, 0xff, sizeof ip);
+    assert(packet_csum_pseudoheader(&ip) == 0x5c2fb);
+
+    mark('#');
+}
 
 static void
 test_csum_main(int argc OVS_UNUSED, char *argv[] OVS_UNUSED)
@@ -239,6 +269,7 @@ test_csum_main(int argc OVS_UNUSED, char *argv[] OVS_UNUSED)
 
     test_rfc1624();
     test_crc32c();
+    test_pseudo();
 
     /* Test recalc_csum16(). */
     for (i = 0; i < 32; i++) {