Fix IPv6 csum calculation in GTP-U encapsulation

The length field is included in the checksum. Therefor, we need
to update it before calculating the checksum.

Change-Id: Id23234efb80ea3747a0f8a5c7bf8621748d27635
Signed-off-by: Andreas Schultz <andreas.schultz@travelping.com>

diff --git a/src/plugins/gtpu/gtpu_encap.c b/src/plugins/gtpu/gtpu_encap.c
index 4442c42..5f52d5a 100644 (file)
--- a/src/plugins/gtpu/gtpu_encap.c
+++ b/src/plugins/gtpu/gtpu_encap.c
@@ -380,24 +380,6 @@ gtpu_encap_inline (vlib_main_t * vm,
              udp3->length = new_l3;
              udp3->src_port = flow_hash3;
 
-             /* IPv6 UDP checksum is mandatory */
-             udp0->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b0,
-                                                                ip6_0, &bogus);
-             if (udp0->checksum == 0)
-               udp0->checksum = 0xffff;
-             udp1->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b1,
-                                                        ip6_1, &bogus);
-             if (udp1->checksum == 0)
-               udp1->checksum = 0xffff;
-             udp2->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b2,
-                                                                ip6_2, &bogus);
-             if (udp2->checksum == 0)
-               udp2->checksum = 0xffff;
-             udp3->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b3,
-                                                        ip6_3, &bogus);
-             if (udp3->checksum == 0)
-               udp3->checksum = 0xffff;
-
              /* Fix GTPU length */
              gtpu0 = (gtpu_header_t *)(udp0+1);
              new_l0 = clib_host_to_net_u16 (vlib_buffer_length_in_chain(vm, b0)
@@ -419,6 +401,25 @@ gtpu_encap_inline (vlib_main_t * vm,
                                             - sizeof (*ip6_3) - sizeof(*udp3)
                                             - GTPU_V1_HDR_LEN);
              gtpu3->length = new_l3;
+
+             /* IPv6 UDP checksum is mandatory */
+             udp0->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b0,
+                                                                ip6_0, &bogus);
+             if (udp0->checksum == 0)
+               udp0->checksum = 0xffff;
+             udp1->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b1,
+                                                                ip6_1, &bogus);
+             if (udp1->checksum == 0)
+               udp1->checksum = 0xffff;
+             udp2->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b2,
+                                                                ip6_2, &bogus);
+             if (udp2->checksum == 0)
+               udp2->checksum = 0xffff;
+             udp3->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b3,
+                                                                ip6_3, &bogus);
+             if (udp3->checksum == 0)
+               udp3->checksum = 0xffff;
+
            }
 
           pkts_encapsulated += 4;
@@ -592,18 +593,18 @@ gtpu_encap_inline (vlib_main_t * vm,
              udp0->length = new_l0;
              udp0->src_port = flow_hash0;
 
-             /* IPv6 UDP checksum is mandatory */
-             udp0->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b0,
-                                                                ip6_0, &bogus);
-             if (udp0->checksum == 0)
-               udp0->checksum = 0xffff;
-
              /* Fix GTPU length */
              gtpu0 = (gtpu_header_t *)(udp0+1);
              new_l0 = clib_host_to_net_u16 (vlib_buffer_length_in_chain(vm, b0)
                                             - sizeof (*ip4_0) - sizeof(*udp0)
                                             - GTPU_V1_HDR_LEN);
              gtpu0->length = new_l0;
+
+             /* IPv6 UDP checksum is mandatory */
+             udp0->checksum = ip6_tcp_udp_icmp_compute_checksum(vm, b0,
+                                                                ip6_0, &bogus);
+             if (udp0->checksum == 0)
+               udp0->checksum = 0xffff;
            }
 
           pkts_encapsulated ++;