reverse-proxy: Add in reverse proxy support to coap-server

Tidy up the general proxy logic by moving common functionality
into libcoap.

New functions coap_proxy_forward_request() and coap_proxy_forward_response()
added.

Support for common shared connection to next hop.

Support for round-robin balancing across multiple next hops.

CMakeLists.txt

@@ -745,6 +745,7 @@ target_sources(
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_oscore.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_pdu.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_prng.c
+          ${CMAKE_CURRENT_LIST_DIR}/src/coap_proxy.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_resource.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_session.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_sha1.c
@@ -784,6 +785,7 @@ target_sources(
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_option.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_pdu.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_prng.h
+          ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_proxy.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_resource.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_session.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_str.h

CMakeLists.txt.in

@@ -745,6 +745,7 @@ target_sources(
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_oscore.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_pdu.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_prng.c
+          ${CMAKE_CURRENT_LIST_DIR}/src/coap_proxy.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_resource.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_session.c
           ${CMAKE_CURRENT_LIST_DIR}/src/coap_sha1.c
@@ -784,6 +785,7 @@ target_sources(
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_option.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_pdu.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_prng.h
+          ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_proxy.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_resource.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_session.h
           ${CMAKE_CURRENT_LIST_DIR}/include/coap${LIBCOAP_API_VERSION}/coap_str.h

Makefile.am

@@ -113,6 +113,7 @@ EXTRA_DIST = \
   include/coap$(LIBCOAP_API_VERSION)/coap_oscore_internal.h \
   include/coap$(LIBCOAP_API_VERSION)/coap_pdu_internal.h \
   include/coap$(LIBCOAP_API_VERSION)/coap_prng_internal.h \
+  include/coap$(LIBCOAP_API_VERSION)/coap_proxy_internal.h \
   include/coap$(LIBCOAP_API_VERSION)/coap_resource_internal.h \
   include/coap$(LIBCOAP_API_VERSION)/coap_session_internal.h \
   include/coap$(LIBCOAP_API_VERSION)/coap_sha1_internal.h \
@@ -211,6 +212,7 @@ libcoap_@LIBCOAP_NAME_SUFFIX@_la_SOURCES = \
   src/coap_option.c \
   src/coap_oscore.c \
   src/coap_pdu.c \
+  src/coap_proxy.c \
   src/coap_prng.c \
   src/coap_resource.c \
   src/coap_session.c \
@@ -260,6 +262,7 @@ libcoap_include_HEADERS = \
   $(top_srcdir)/include/coap$(LIBCOAP_API_VERSION)/coap_oscore.h \
   $(top_srcdir)/include/coap$(LIBCOAP_API_VERSION)/coap_pdu.h \
   $(top_srcdir)/include/coap$(LIBCOAP_API_VERSION)/coap_prng.h \
+  $(top_srcdir)/include/coap$(LIBCOAP_API_VERSION)/coap_proxy.h \
   $(top_srcdir)/include/coap$(LIBCOAP_API_VERSION)/coap_resource.h \
   $(top_srcdir)/include/coap$(LIBCOAP_API_VERSION)/coap_session.h \
   $(top_srcdir)/include/coap$(LIBCOAP_API_VERSION)/coap_str.h \

configure.ac

@@ -1337,6 +1337,7 @@ man/coap_oscore.txt
 man/coap_pdu_access.txt
 man/coap_pdu_setup.txt
 man/coap_persist.txt
+man/coap_proxy.txt
 man/coap_recovery.txt
 man/coap_resource.txt
 man/coap_session.txt