sr: add "set sr encaps hop-limit" command

Default hop-limit for the encapsulating IPv6 header is a compile-time
constant. Add ability to specify custom hop-limit, in order to avoid
packets being dropped with "hop limit exceeded in transit" response in
certain network configurations.

Type: feature
Signed-off-by: Ignas Bačius <ignas@noia.network>
Change-Id: I77f2b35c987cfd31801dc2744d31fb3c1984158f

1 files changed, 40 insertions, 1 deletions

diff --git a/src/vnet/srv6/sr_policy_rewrite.c b/src/vnet/srv6/sr_policy_rewrite.c
index feac151665a..8d11da67ddf 100755
--- a/src/vnet/srv6/sr_policy_rewrite.c
+++ b/src/vnet/srv6/sr_policy_rewrite.c
@@ -107,6 +107,7 @@ static dpo_type_t sr_pr_bsid_insert_dpo_type;
  * @brief IPv6 SA for encapsulated packets
  */
 static ip6_address_t sr_pr_encaps_src;
+static u8 sr_pr_encaps_hop_limit = IPv6_DEFAULT_HOP_LIMIT;
 
 /******************* SR rewrite set encaps IPv6 source addr *******************/
 /* Note:  This is temporal. We don't know whether to follow this path or
@@ -141,6 +142,44 @@ VLIB_CLI_COMMAND (set_sr_src_command, static) = {
 };
 /* *INDENT-ON* */
 
+/******************** SR rewrite set encaps IPv6 hop-limit ********************/
+
+void
+sr_set_hop_limit (u8 hop_limit)
+{
+  sr_pr_encaps_hop_limit = hop_limit;
+}
+
+u8
+sr_get_hop_limit (void)
+{
+  return sr_pr_encaps_hop_limit;
+}
+
+static clib_error_t *
+set_sr_hop_limit_command_fn (vlib_main_t * vm, unformat_input_t * input,
+			     vlib_cli_command_t * cmd)
+{
+  int hop_limit = sr_get_hop_limit ();
+
+  if (unformat_check_input (input) == UNFORMAT_END_OF_INPUT)
+    return clib_error_return (0, "No value specified");
+  if (!unformat (input, "%d", &hop_limit))
+    return clib_error_return (0, "Invalid value");
+  if (hop_limit <= 0 || hop_limit > 255)
+    return clib_error_return (0, "Value out of range [1-255]");
+  sr_pr_encaps_hop_limit = (u8) hop_limit;
+  return 0;
+}
+
+/* *INDENT-OFF* */
+VLIB_CLI_COMMAND (set_sr_hop_limit_command, static) = {
+  .path = "set sr encaps hop-limit",
+  .short_help = "set sr encaps hop-limit <value>",
+  .function = set_sr_hop_limit_command_fn,
+};
+/* *INDENT-ON* */
+
 /*********************** SR rewrite string computation ************************/
 /**
  * @brief SR rewrite string computation for IPv6 encapsulation (inline)
@@ -175,7 +214,7 @@ compute_rewrite_encaps (ip6_address_t * sl)
   iph->src_address.as_u64[1] = sr_pr_encaps_src.as_u64[1];
   iph->payload_length = header_length - IPv6_DEFAULT_HEADER_LENGTH;
   iph->protocol = IP_PROTOCOL_IPV6;
-  iph->hop_limit = IPv6_DEFAULT_HOP_LIMIT;
+  iph->hop_limit = sr_pr_encaps_hop_limit;
 
   if (vec_len (sl) > 1)
     {