nat: ICMP handling fixes

If ICMP comes from a router on path, source address must not be
rewritten in o2i path to avoid getting wrong checksum.

Fix ICMP checksum computations.

Type: fix
Signed-off-by: Klement Sekera <ksekera@cisco.com>
Change-Id: I035debccf966d7dbd63c364cb1e43380d641f708

diff --git a/src/plugins/nat/nat44-ed/nat44_ed.c b/src/plugins/nat/nat44-ed/nat44_ed.c
index d42d303..1a996cd 100644 (file)
--- a/src/plugins/nat/nat44-ed/nat44_ed.c
+++ b/src/plugins/nat/nat44-ed/nat44_ed.c
@@ -3276,7 +3276,7 @@ static_always_inline int nat_6t_flow_icmp_translate (snat_main_t *sm,
 static_always_inline void
 nat_6t_flow_ip4_translate (snat_main_t *sm, vlib_buffer_t *b, ip4_header_t *ip,
                           nat_6t_flow_t *f, nat_protocol_t proto,
-                          int is_icmp_inner_ip4)
+                          int is_icmp_inner_ip4, int skip_saddr_rewrite)
 {
   udp_header_t *udp = ip4_next_header (ip);
   tcp_header_t *tcp = (tcp_header_t *) udp;
@@ -3319,7 +3319,10 @@ nat_6t_flow_ip4_translate (snat_main_t *sm, vlib_buffer_t *b, ip4_header_t *ip,
     {
       if (!is_icmp_inner_ip4)
        { // regular case
-         ip->src_address = f->rewrite.saddr;
+         if (!skip_saddr_rewrite)
+           {
+             ip->src_address = f->rewrite.saddr;
+           }
          ip->dst_address = f->rewrite.daddr;
        }
       else
@@ -3329,9 +3332,16 @@ nat_6t_flow_ip4_translate (snat_main_t *sm, vlib_buffer_t *b, ip4_header_t *ip,
        }
     }
 
-  ip_csum_t ip_sum = ip->checksum;
-  ip_sum = ip_csum_sub_even (ip_sum, f->l3_csum_delta);
-  ip->checksum = ip_csum_fold (ip_sum);
+  if (skip_saddr_rewrite)
+    {
+      ip->checksum = ip4_header_checksum (ip);
+    }
+  else
+    {
+      ip_csum_t ip_sum = ip->checksum;
+      ip_sum = ip_csum_sub_even (ip_sum, f->l3_csum_delta);
+      ip->checksum = ip_csum_fold (ip_sum);
+    }
   if (0xffff == ip->checksum)
     ip->checksum = 0;
   ASSERT (ip4_header_checksum_is_valid (ip));
@@ -3378,16 +3388,53 @@ nat_6t_flow_icmp_translate (snat_main_t *sm, vlib_buffer_t *b,
          nat_protocol_t inner_proto =
            ip_proto_to_nat_proto (inner_ip->protocol);
 
-         ip_csum_t icmp_sum = icmp->checksum;
+         ip_csum_t old_icmp_sum = icmp->checksum;
+         ip_csum_t old_inner_ip_sum = inner_ip->checksum;
+         ip_csum_t old_udp_sum;
+         ip_csum_t old_tcp_sum;
+         ip_csum_t new_icmp_sum;
+         udp_header_t *udp;
+         tcp_header_t *tcp;
 
          switch (inner_proto)
            {
            case NAT_PROTOCOL_UDP:
+             udp = (udp_header_t *) (inner_ip + 1);
+             old_udp_sum = udp->checksum;
+             nat_6t_flow_ip4_translate (sm, b, inner_ip, f, inner_proto,
+                                        1 /* is_icmp_inner_ip4 */,
+                                        0 /* skip_saddr_rewrite */);
+             new_icmp_sum = ip_csum_sub_even (old_icmp_sum, f->l3_csum_delta);
+             new_icmp_sum = ip_csum_sub_even (new_icmp_sum, f->l4_csum_delta);
+             new_icmp_sum =
+               ip_csum_update (new_icmp_sum, old_inner_ip_sum,
+                               inner_ip->checksum, ip4_header_t, checksum);
+             new_icmp_sum =
+               ip_csum_update (new_icmp_sum, old_udp_sum, udp->checksum,
+                               udp_header_t, checksum);
+             new_icmp_sum = ip_csum_fold (new_icmp_sum);
+             if (0xffff == new_icmp_sum)
+               new_icmp_sum = 0;
+             icmp->checksum = new_icmp_sum;
+             break;
            case NAT_PROTOCOL_TCP:
+             tcp = (tcp_header_t *) (inner_ip + 1);
+             old_tcp_sum = tcp->checksum;
              nat_6t_flow_ip4_translate (sm, b, inner_ip, f, inner_proto,
-                                        1 /* is_icmp_inner_ip4 */);
-             icmp_sum = ip_csum_sub_even (icmp_sum, f->l3_csum_delta);
-             icmp->checksum = ip_csum_fold (icmp_sum);
+                                        1 /* is_icmp_inner_ip4 */,
+                                        0 /* skip_saddr_rewrite */);
+             new_icmp_sum = ip_csum_sub_even (old_icmp_sum, f->l3_csum_delta);
+             new_icmp_sum = ip_csum_sub_even (new_icmp_sum, f->l4_csum_delta);
+             new_icmp_sum =
+               ip_csum_update (new_icmp_sum, old_inner_ip_sum,
+                               inner_ip->checksum, ip4_header_t, checksum);
+             new_icmp_sum =
+               ip_csum_update (new_icmp_sum, old_tcp_sum, tcp->checksum,
+                               tcp_header_t, checksum);
+             new_icmp_sum = ip_csum_fold (new_icmp_sum);
+             if (0xffff == new_icmp_sum)
+               new_icmp_sum = 0;
+             icmp->checksum = new_icmp_sum;
              break;
            case NAT_PROTOCOL_ICMP:
              if (f->ops & NAT_FLOW_OP_ICMP_ID_REWRITE)
@@ -3417,29 +3464,63 @@ nat_6t_flow_icmp_translate (snat_main_t *sm, vlib_buffer_t *b,
            }
        }
     }
+
   return NAT_ED_TRNSL_ERR_SUCCESS;
 }
 
-nat_translation_error_e
+static_always_inline nat_translation_error_e
 nat_6t_flow_buf_translate (snat_main_t *sm, vlib_buffer_t *b, ip4_header_t *ip,
                           nat_6t_flow_t *f, nat_protocol_t proto,
-                          int is_output_feature)
+                          int is_output_feature, int is_i2o)
 {
   if (!is_output_feature && f->ops & NAT_FLOW_OP_TXFIB_REWRITE)
     {
       vnet_buffer (b)->sw_if_index[VLIB_TX] = f->rewrite.fib_index;
     }
 
-  nat_6t_flow_ip4_translate (sm, b, ip, f, proto, 0 /* is_icmp_inner_ip4 */);
-
   if (NAT_PROTOCOL_ICMP == proto)
     {
+      if (ip->src_address.as_u32 != f->rewrite.saddr.as_u32)
+       {
+         // packet is returned from a router, not from destination
+         // skip source address rewrite if in o2i path
+         nat_6t_flow_ip4_translate (sm, b, ip, f, proto,
+                                    0 /* is_icmp_inner_ip4 */,
+                                    !is_i2o /* skip_saddr_rewrite */);
+       }
+      else
+       {
+         nat_6t_flow_ip4_translate (sm, b, ip, f, proto,
+                                    0 /* is_icmp_inner_ip4 */,
+                                    0 /* skip_saddr_rewrite */);
+       }
       return nat_6t_flow_icmp_translate (sm, b, ip, f);
     }
 
+  nat_6t_flow_ip4_translate (sm, b, ip, f, proto, 0 /* is_icmp_inner_ip4 */,
+                            0 /* skip_saddr_rewrite */);
+
   return NAT_ED_TRNSL_ERR_SUCCESS;
 }
 
+nat_translation_error_e
+nat_6t_flow_buf_translate_i2o (snat_main_t *sm, vlib_buffer_t *b,
+                              ip4_header_t *ip, nat_6t_flow_t *f,
+                              nat_protocol_t proto, int is_output_feature)
+{
+  return nat_6t_flow_buf_translate (sm, b, ip, f, proto, is_output_feature,
+                                   1 /* is_i2o */);
+}
+
+nat_translation_error_e
+nat_6t_flow_buf_translate_o2i (snat_main_t *sm, vlib_buffer_t *b,
+                              ip4_header_t *ip, nat_6t_flow_t *f,
+                              nat_protocol_t proto, int is_output_feature)
+{
+  return nat_6t_flow_buf_translate (sm, b, ip, f, proto, is_output_feature,
+                                   0 /* is_i2o */);
+}
+
 u8 *
 format_nat_6t (u8 *s, va_list *args)
 {

diff --git a/src/plugins/nat/nat44-ed/nat44_ed.h b/src/plugins/nat/nat44-ed/nat44_ed.h
index 2710d29..420f84c 100644 (file)
--- a/src/plugins/nat/nat44-ed/nat44_ed.h
+++ b/src/plugins/nat/nat44-ed/nat44_ed.h
@@ -1153,9 +1153,14 @@ typedef enum
 } nat_translation_error_e;
 
 nat_translation_error_e
-nat_6t_flow_buf_translate (snat_main_t *sm, vlib_buffer_t *b, ip4_header_t *ip,
-                          nat_6t_flow_t *f, nat_protocol_t proto,
-                          int is_output_feature);
+nat_6t_flow_buf_translate_i2o (snat_main_t *sm, vlib_buffer_t *b,
+                              ip4_header_t *ip, nat_6t_flow_t *f,
+                              nat_protocol_t proto, int is_output_feature);
+
+nat_translation_error_e
+nat_6t_flow_buf_translate_o2i (snat_main_t *sm, vlib_buffer_t *b,
+                              ip4_header_t *ip, nat_6t_flow_t *f,
+                              nat_protocol_t proto, int is_output_feature);
 
 void nat_6t_l3_l4_csum_calc (nat_6t_flow_t *f);
 

diff --git a/src/plugins/nat/nat44-ed/nat44_ed_in2out.c b/src/plugins/nat/nat44-ed/nat44_ed_in2out.c
index 426b6ee..f7257db 100644 (file)
--- a/src/plugins/nat/nat44-ed/nat44_ed_in2out.c
+++ b/src/plugins/nat/nat44-ed/nat44_ed_in2out.c
@@ -1183,7 +1183,7 @@ nat44_ed_in2out_fast_path_node_fn_inline (vlib_main_t *vm,
        }
 
       if (NAT_ED_TRNSL_ERR_SUCCESS !=
-         (translation_error = nat_6t_flow_buf_translate (
+         (translation_error = nat_6t_flow_buf_translate_i2o (
             sm, b0, ip0, f, proto0, is_output_feature)))
        {
          nat_free_session_data (sm, s0, thread_index, 0);
@@ -1331,7 +1331,7 @@ nat44_ed_in2out_slow_path_node_fn_inline (vlib_main_t *vm,
 
          if (NAT_NEXT_DROP != next[0] && s0 &&
              NAT_ED_TRNSL_ERR_SUCCESS !=
-               (translation_error = nat_6t_flow_buf_translate (
+               (translation_error = nat_6t_flow_buf_translate_i2o (
                   sm, b0, ip0, &s0->i2o, proto0, is_output_feature)))
            {
              goto trace0;
@@ -1349,7 +1349,7 @@ nat44_ed_in2out_slow_path_node_fn_inline (vlib_main_t *vm,
            now, thread_index, proto0, &s0, is_multi_worker);
          if (NAT_NEXT_DROP != next[0] && s0 &&
              NAT_ED_TRNSL_ERR_SUCCESS !=
-               (translation_error = nat_6t_flow_buf_translate (
+               (translation_error = nat_6t_flow_buf_translate_i2o (
                   sm, b0, ip0, &s0->i2o, proto0, is_output_feature)))
            {
              goto trace0;
@@ -1426,7 +1426,7 @@ nat44_ed_in2out_slow_path_node_fn_inline (vlib_main_t *vm,
       b0->flags |= VNET_BUFFER_F_IS_NATED;
 
       if (NAT_ED_TRNSL_ERR_SUCCESS !=
-         (translation_error = nat_6t_flow_buf_translate (
+         (translation_error = nat_6t_flow_buf_translate_i2o (
             sm, b0, ip0, &s0->i2o, proto0, is_output_feature)))
        {
          nat_free_session_data (sm, s0, thread_index, 0);

diff --git a/src/plugins/nat/nat44-ed/nat44_ed_out2in.c b/src/plugins/nat/nat44-ed/nat44_ed_out2in.c
index f14311a..995260a 100644 (file)
--- a/src/plugins/nat/nat44-ed/nat44_ed_out2in.c
+++ b/src/plugins/nat/nat44-ed/nat44_ed_out2in.c
@@ -1026,7 +1026,7 @@ nat44_ed_out2in_fast_path_node_fn_inline (vlib_main_t * vm,
        }
 
       if (NAT_ED_TRNSL_ERR_SUCCESS !=
-         (translation_error = nat_6t_flow_buf_translate (
+         (translation_error = nat_6t_flow_buf_translate_o2i (
             sm, b0, ip0, f, proto0, 0 /* is_output_feature */)))
        {
          next[0] = NAT_NEXT_DROP;
@@ -1182,7 +1182,7 @@ nat44_ed_out2in_slow_path_node_fn_inline (vlib_main_t * vm,
            }
          if (NAT_NEXT_DROP != next[0] && s0 &&
              NAT_ED_TRNSL_ERR_SUCCESS !=
-               (translation_error = nat_6t_flow_buf_translate (
+               (translation_error = nat_6t_flow_buf_translate_o2i (
                   sm, b0, ip0, &s0->o2i, proto0, 0 /* is_output_feature */)))
            {
              goto trace0;
@@ -1201,7 +1201,7 @@ nat44_ed_out2in_slow_path_node_fn_inline (vlib_main_t * vm,
 
          if (NAT_NEXT_DROP != next[0] && s0 &&
              NAT_ED_TRNSL_ERR_SUCCESS !=
-               (translation_error = nat_6t_flow_buf_translate (
+               (translation_error = nat_6t_flow_buf_translate_o2i (
                   sm, b0, ip0, &s0->o2i, proto0, 0 /* is_output_feature */)))
            {
              goto trace0;
@@ -1311,7 +1311,7 @@ nat44_ed_out2in_slow_path_node_fn_inline (vlib_main_t * vm,
        }
 
       if (NAT_ED_TRNSL_ERR_SUCCESS !=
-         (translation_error = nat_6t_flow_buf_translate (
+         (translation_error = nat_6t_flow_buf_translate_o2i (
             sm, b0, ip0, &s0->o2i, proto0, 0 /* is_output_feature */)))
        {
          next[0] = NAT_NEXT_DROP;