TCP: CR: fix corner case for Context Replication

Corner case is:
1/ Send IR packet for stream CID=0
2/ Receive ACK for CID=0, making the stream 'established'
3/ Send IR-CR packet for stream CID=1, with base CID=0 (as CID=0 is
   established), but lose the packet in the way towards decompressor
4/ Send a new packet for CID=0, but with TTL changed (+1)
5/ Send a new packet for CID=1, IR-CR is repeated since previous IR-CR
   was lost and no ACK was received
6/ Decompressor fails to decompress packet IR-CR

The problem was located at compressor. At step 5, the compressor used a
copy of context CID=0 as base context instead of the real context CID=0.

The problem was fixed by using the base context as reference while:
a/ finding differences between the context and the packet,
b/ determining the best packet type to build, and
c/ while building the packet.
The real context is only used while updating the context.

To achieve that, all steps a/ b/ c/ were reworked not to modify the
context. 49 commits were required. Once rework was achieved, the fix is
quite simple.

src/comp/c_tcp_dynamic.c

@@ -67,7 +67,8 @@ static int tcp_code_dynamic_tcp_part(const struct rohc_comp_ctxt *const context,
 /**
  * @brief Code the dynamic part of an IR or IR-DYN packet
  *
- * @param context           The compression context
+ * @param context           The real compression context for traces and update
+ * @param ref_ctxt          The reference compression context to detect changes
  * @param uncomp_pkt_hdrs   The uncompressed headers to encode
  * @param tmp               The temporary state for compressed packet
  * @param rohc_pkt          OUT: The ROHC packet
@@ -76,12 +77,13 @@ static int tcp_code_dynamic_tcp_part(const struct rohc_comp_ctxt *const context,
  *                          -1 otherwise
  */
 int tcp_code_dyn_part(const struct rohc_comp_ctxt *const context,
+                      const struct rohc_comp_ctxt *const ref_ctxt,
                       const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                       const struct tcp_tmp_variables *const tmp,
                       uint8_t *const rohc_pkt,
                       const size_t rohc_pkt_max_len)
 {
-	const struct sc_tcp_context *const tcp_context = context->specific;
+	const struct sc_tcp_context *const tcp_context = ref_ctxt->specific;
 
 	uint8_t *rohc_remain_data = rohc_pkt;
 	size_t rohc_remain_len = rohc_pkt_max_len;
@@ -173,7 +175,7 @@ int tcp_code_dyn_part(const struct rohc_comp_ctxt *const context,
 /**
  * @brief Build the dynamic part of the IPv4 header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param ip_context      The specific IP compression context
  * @param ipv4            The IPv4 header
  * @param ip_id_behavior  The IP-ID behavior of the IPv4 header
@@ -254,7 +256,7 @@ static int tcp_code_dynamic_ipv4_part(const struct rohc_comp_ctxt *const context
 /**
  * @brief Build the dynamic part of the IPv6 header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param ip_context      The specific IP compression context
  * @param ipv6            The IPv6 header
  * @param[out] rohc_data  The ROHC packet being built
@@ -366,7 +368,7 @@ TODO
 
 \endverbatim
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param uncomp_pkt_hdrs The uncompressed headers to encode
  * @param tmp             The temporary state for compressed packet
  * @param[out] rohc_data  The ROHC packet being built

src/comp/c_tcp_dynamic.h

@@ -37,11 +37,12 @@
 #include <stdlib.h>
 
 int tcp_code_dyn_part(const struct rohc_comp_ctxt *const context,
+                      const struct rohc_comp_ctxt *const ref_ctxt,
                       const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                       const struct tcp_tmp_variables *const tmp,
                       uint8_t *const rohc_pkt,
                       const size_t rohc_pkt_max_len)
-	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4)));
+	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4, 5)));
 
 #endif /* ROHC_COMP_TCP_DYNAMIC_H */
 

src/comp/c_tcp_irregular.c

@@ -63,18 +63,20 @@ static int tcp_code_irregular_ipv6_opt_part(const struct rohc_comp_ctxt *const c
 	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4)));
 
 static int tcp_code_irregular_tcp_part(const struct rohc_comp_ctxt *const context,
+                                       const struct rohc_comp_ctxt *const ref_ctxt,
                                        const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                                        const struct tcp_tmp_variables *const tmp,
                                        const uint8_t ip_inner_ecn,
                                        uint8_t *const rohc_data,
                                        const size_t rohc_max_len)
-	__attribute__((warn_unused_result, nonnull(1, 2, 3, 5)));
+	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4, 6)));
 
 
 /**
  * @brief Code the irregular chain of one CO packet
  *
- * @param context           The compression context
+ * @param context           The real compression context for traces and update
+ * @param ref_ctxt          The reference compression context to detect changes
  * @param uncomp_pkt_hdrs   The uncompressed headers to encode
  * @param tmp               The temporary state for the compressed packet
  * @param rohc_pkt          OUT: The ROHC packet
@@ -83,12 +85,13 @@ static int tcp_code_irregular_tcp_part(const struct rohc_comp_ctxt *const contex
  *                          -1 otherwise
  */
 int tcp_code_irreg_chain(const struct rohc_comp_ctxt *const context,
+                         const struct rohc_comp_ctxt *const ref_ctxt,
                          const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                          const struct tcp_tmp_variables *const tmp,
                          uint8_t *const rohc_pkt,
                          const size_t rohc_pkt_max_len)
 {
-	const struct sc_tcp_context *const tcp_context = context->specific;
+	const struct sc_tcp_context *const tcp_context = ref_ctxt->specific;
 	uint8_t *rohc_remain_data = rohc_pkt;
 	size_t rohc_remain_len = rohc_pkt_max_len;
 	uint8_t ip_inner_ecn;
@@ -177,8 +180,8 @@ int tcp_code_irreg_chain(const struct rohc_comp_ctxt *const context,
 	}
 
 	/* TCP part (base header + options) of the irregular chain */
-	ret = tcp_code_irregular_tcp_part(context, uncomp_pkt_hdrs, tmp, ip_inner_ecn,
-	                                  rohc_remain_data, rohc_remain_len);
+	ret = tcp_code_irregular_tcp_part(context, ref_ctxt, uncomp_pkt_hdrs, tmp,
+	                                  ip_inner_ecn, rohc_remain_data, rohc_remain_len);
 	if(ret < 0)
 	{
 		rohc_comp_warn(context, "failed to build the TCP header part "
@@ -202,7 +205,7 @@ int tcp_code_irreg_chain(const struct rohc_comp_ctxt *const context,
  *
  * See RFC 4996 page 63
  *
- * @param context               The compression context
+ * @param context               The real compression context for traces and update
  * @param ip_context            The specific IP compression context
  * @param ipv4                  The IPv4 header
  * @param ip_id_behavior        The IP-ID behavior of the IPv4 header
@@ -305,7 +308,7 @@ static int tcp_code_irregular_ipv4_part(const struct rohc_comp_ctxt *const conte
  *
  * See RFC 4996 page 63
  *
- * @param context               The compression context
+ * @param context               The real compression context for traces and update
  * @param ip_context            The specific IP compression context
  * @param ipv6                  The IPv6 header
  * @param is_innermost          True if IP header is the innermost of the packet
@@ -387,15 +390,15 @@ static int tcp_code_irregular_ipv6_part(const struct rohc_comp_ctxt *const conte
 /**
  * @brief Build the irregular part of the IPv6 option header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param opt_ctxt        The compression context of the IPv6 option
  * @param ext             The IPv6 extension header
  * @param[out] rohc_data  The ROHC packet being built
  * @param rohc_max_len    The max remaining length in the ROHC buffer
  * @return                The length appended in the ROHC buffer if positive,
  *                        -1 in case of error
  */
-static int tcp_code_irregular_ipv6_opt_part(const struct rohc_comp_ctxt *const context __attribute__((unused)),
+static int tcp_code_irregular_ipv6_opt_part(const struct rohc_comp_ctxt *const context,
                                             const ip_option_context_t *const opt_ctxt __attribute__((unused)),
                                             const struct rohc_pkt_ip_ext_hdr *const ext,
                                             uint8_t *const rohc_data __attribute__((unused)),
@@ -424,7 +427,8 @@ static int tcp_code_irregular_ipv6_opt_part(const struct rohc_comp_ctxt *const c
 /**
  * @brief Build the irregular part of the TCP header.
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
+ * @param ref_ctxt        The reference compression context to detect changes
  * @param uncomp_pkt_hdrs The uncompressed headers to encode
  * @param tmp             The temporary state for compressed packet
  * @param ip_inner_ecn    The ECN flags of the innermost IP header
@@ -434,13 +438,14 @@ static int tcp_code_irregular_ipv6_opt_part(const struct rohc_comp_ctxt *const c
  *                        -1 in case of error
  */
 static int tcp_code_irregular_tcp_part(const struct rohc_comp_ctxt *const context,
+                                       const struct rohc_comp_ctxt *const ref_ctxt,
                                        const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                                        const struct tcp_tmp_variables *const tmp,
                                        const uint8_t ip_inner_ecn,
                                        uint8_t *const rohc_data,
                                        const size_t rohc_max_len)
 {
-	const struct sc_tcp_context *const tcp_context = context->specific;
+	const struct sc_tcp_context *const tcp_context = ref_ctxt->specific;
 	const struct tcphdr *const tcp = (struct tcphdr *) uncomp_pkt_hdrs->tcp;
 	uint8_t *rohc_remain_data = rohc_data;
 	size_t rohc_remain_len = rohc_max_len;

src/comp/c_tcp_irregular.h

@@ -38,11 +38,12 @@
 #include <stdlib.h>
 
 int tcp_code_irreg_chain(const struct rohc_comp_ctxt *const context,
+                         const struct rohc_comp_ctxt *const ref_ctxt,
                          const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                          const struct tcp_tmp_variables *const tmp,
                          uint8_t *const rohc_pkt,
                          const size_t rohc_pkt_max_len)
-	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4)));
+	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4, 5)));
 
 #endif /* ROHC_COMP_TCP_IRREGULAR_H */
 

src/comp/c_tcp_opts_list.c

@@ -738,7 +738,7 @@ void tcp_detect_options_changes(const struct rohc_comp_ctxt *const context,
  *  - the replicate chain of the IR-CR packets,
  *  - at the end of the rnd_8, seq_8, and co_common packets.
  *
- * @param context            The compression context
+ * @param context            The real compression context for traces and update
  * @param uncomp_pkt_hdrs    The uncompressed headers to encode
  * @param tmp                The temporary state for compressed TCP options
  * @param items_needed       Whether items shall be transmitted or not

src/comp/c_tcp_replicate.c

@@ -54,17 +54,19 @@ static int tcp_code_replicate_ipv6_opt_part(const struct rohc_comp_ctxt *const c
 	__attribute__((warn_unused_result, nonnull(1, 2, 3)));
 
 static int tcp_code_replicate_tcp_part(const struct rohc_comp_ctxt *const context,
+                                       const struct rohc_comp_ctxt *const ref_ctxt,
                                        const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                                        const struct tcp_tmp_variables *const tmp,
                                        uint8_t *const rohc_data,
                                        const size_t rohc_max_len)
-	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4)));
+	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4, 5)));
 
 
 /**
  * @brief Code the replicate chain of an IR packet
  *
- * @param context           The compression context
+ * @param context           The real compression context for traces and update
+ * @param ref_ctxt          The reference compression context to detect changes
  * @param uncomp_pkt_hdrs   The uncompressed headers to encode
  * @param tmp               The temporary state for the compressed packet
  * @param[out] rohc_pkt     The ROHC packet being built
@@ -73,12 +75,13 @@ static int tcp_code_replicate_tcp_part(const struct rohc_comp_ctxt *const contex
  *                          -1 otherwise
  */
 int tcp_code_replicate_chain(const struct rohc_comp_ctxt *const context,
+                             const struct rohc_comp_ctxt *const ref_ctxt,
                              const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                              const struct tcp_tmp_variables *const tmp,
                              uint8_t *const rohc_pkt,
                              const size_t rohc_pkt_max_len)
 {
-	const struct sc_tcp_context *const tcp_context = context->specific;
+	const struct sc_tcp_context *const tcp_context = ref_ctxt->specific;
 
 	uint8_t *rohc_remain_data = rohc_pkt;
 	size_t rohc_remain_len = rohc_pkt_max_len;
@@ -148,7 +151,7 @@ int tcp_code_replicate_chain(const struct rohc_comp_ctxt *const context,
 	}
 
 	/* add TCP replicate part */
-	ret = tcp_code_replicate_tcp_part(context, uncomp_pkt_hdrs, tmp,
+	ret = tcp_code_replicate_tcp_part(context, ref_ctxt, uncomp_pkt_hdrs, tmp,
 	                                  rohc_remain_data, rohc_remain_len);
 	if(ret < 0)
 	{
@@ -171,7 +174,7 @@ int tcp_code_replicate_chain(const struct rohc_comp_ctxt *const context,
 /**
  * @brief Build the replicate part of the IPv4 header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param ip_context      The specific IP compression context
  * @param ipv4            The IPv4 header
  * @param ip_id_behavior  The IP-ID behavior of the IPv4 header
@@ -261,7 +264,7 @@ static int tcp_code_replicate_ipv4_part(const struct rohc_comp_ctxt *const conte
 /**
  * @brief Build the replicate part of the IPv6 header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param ip_context      The specific IP compression context
  * @param ipv6            The IPv6 header
  * @param[out] rohc_data  The ROHC packet being built
@@ -332,7 +335,7 @@ static int tcp_code_replicate_ipv6_part(const struct rohc_comp_ctxt *const conte
 /**
  * @brief Build the replicate part of the IPv6 option header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param ext             The IPv6 extension header
  * @param[out] rohc_data  The ROHC packet being built
  * @param rohc_max_len    The max remaining length in the ROHC buffer
@@ -390,7 +393,8 @@ static int tcp_code_replicate_ipv6_opt_part(const struct rohc_comp_ctxt *const c
 /**
  * @brief Build the replicate part of the TCP header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
+ * @param ref_ctxt        The reference compression context to detect changes
  * @param uncomp_pkt_hdrs The uncompressed headers to encode
  * @param tmp             The temporary state for the compressed packet
  * @param[out] rohc_data  The ROHC packet being built
@@ -399,13 +403,14 @@ static int tcp_code_replicate_ipv6_opt_part(const struct rohc_comp_ctxt *const c
  *                        -1 in case of error
  */
 static int tcp_code_replicate_tcp_part(const struct rohc_comp_ctxt *const context,
+                                       const struct rohc_comp_ctxt *const ref_ctxt,
                                        const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                                        const struct tcp_tmp_variables *const tmp,
                                        uint8_t *const rohc_data,
                                        const size_t rohc_max_len)
 {
 	const uint8_t oa_repetitions_nr = context->compressor->oa_repetitions_nr;
-	const struct sc_tcp_context *const tcp_context = context->specific;
+	const struct sc_tcp_context *const tcp_context = ref_ctxt->specific;
 	const struct tcphdr *const tcp = (struct tcphdr *) uncomp_pkt_hdrs->tcp;
 
 	uint8_t *rohc_remain_data = rohc_data;

src/comp/c_tcp_replicate.h

@@ -33,11 +33,12 @@
 #include <stdlib.h>
 
 int tcp_code_replicate_chain(const struct rohc_comp_ctxt *const context,
+                             const struct rohc_comp_ctxt *const ref_ctxt,
                              const struct rohc_pkt_hdrs *const uncomp_pkt_hdrs,
                              const struct tcp_tmp_variables *const tmp,
                              uint8_t *const rohc_pkt,
                              const size_t rohc_pkt_max_len)
-	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4)));
+	__attribute__((warn_unused_result, nonnull(1, 2, 3, 4, 5)));
 
 #endif /* ROHC_COMP_TCP_REPLICATE_H */
 

src/comp/c_tcp_static.c

@@ -62,7 +62,7 @@ static int tcp_code_static_tcp_part(const struct rohc_comp_ctxt *const context,
 /**
  * @brief Code the static part of an IR packet
  *
- * @param context           The compression context
+ * @param context           The real compression context for traces and update
  * @param uncomp_pkt_hdrs   The uncompressed headers to encode
  * @param rohc_pkt          OUT: The ROHC packet
  * @param rohc_pkt_max_len  The maximum length of the ROHC packet
@@ -158,7 +158,7 @@ int tcp_code_static_part(const struct rohc_comp_ctxt *const context,
 /**
  * @brief Build the static part of the IPv4 header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param ipv4            The IPv4 header
  * @param[out] rohc_data  The ROHC packet being built
  * @param rohc_max_len    The max remaining length in the ROHC buffer
@@ -200,7 +200,7 @@ static int tcp_code_static_ipv4_part(const struct rohc_comp_ctxt *const context,
 /**
  * @brief Build the static part of the IPv6 header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param ipv6            The IPv6 header
  * @param[out] rohc_data  The ROHC packet being built
  * @param rohc_max_len    The max remaining length in the ROHC buffer
@@ -271,7 +271,7 @@ static int tcp_code_static_ipv6_part(const struct rohc_comp_ctxt *const context,
 /**
  * @brief Build the static part of the IPv6 option header
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param ext             The IPv6 extension header
  * @param[out] rohc_data  The ROHC packet being built
  * @param rohc_max_len    The max remaining length in the ROHC buffer
@@ -357,7 +357,7 @@ static int tcp_code_static_ipv6_opt_part(const struct rohc_comp_ctxt *const cont
 
 \endverbatim
  *
- * @param context         The compression context
+ * @param context         The real compression context for traces and update
  * @param tcp             The TCP header
  * @param[out] rohc_data  The ROHC packet being built
  * @param rohc_max_len    The max remaining length in the ROHC buffer

src/comp/rohc_comp.c

@@ -3460,15 +3460,13 @@ static struct rohc_comp_ctxt *
 
 		/* copy the base context, then reset some parts of it */
 		memcpy(c, base_ctxt, sizeof(struct rohc_comp_ctxt));
-		c->do_ctxt_replication = true;
 		c->cr_base_cid = base_ctxt->cid;
 		c->state = ROHC_COMP_STATE_CR;
 	}
 	else
 	{
 		rohc_debug(comp, ROHC_TRACE_COMP, ROHC_PROFILE_GENERAL,
 		           "create context with CID %u without replication", cid_to_use);
-		c->do_ctxt_replication = false;
 		c->state = ROHC_COMP_STATE_IR;
 	}
 
@@ -3500,7 +3498,7 @@ static struct rohc_comp_ctxt *
 	c->compressor = comp;
 
 	/* create profile-specific context */
-	if(c->do_ctxt_replication)
+	if(c->state == ROHC_COMP_STATE_CR)
 	{
 		if(!profile->clone(c, base_ctxt))
 		{
@@ -3755,7 +3753,6 @@ static struct rohc_comp_ctxt *
 		 * is in action, check that the base context didn't change too much */
 		if(context != NULL &&
 		   profile->id == ROHCv1_PROFILE_IP_TCP && /* TODO: replace TCP by CR capacity */
-		   context->do_ctxt_replication &&
 		   context->state == ROHC_COMP_STATE_CR &&
 		   context->state_oa_repeat_nr < comp->oa_repetitions_nr)
 		{

src/comp/rohc_comp_internals.h

@@ -301,8 +301,6 @@ struct rohc_comp_ctxt
 	/** Profile-specific data, defined by the profiles */
 	void *specific;
 
-	/** Whether Context Replication (CR) may be used */
-	bool do_ctxt_replication;
 	/** The base context for Context Replication (CR) */
 	rohc_cid_t cr_base_cid;