ipcpd: Add congestion avoidance policies

This adds congestion avoidance policies to the unicast IPCP.  The
default policy is a multi-bit explicit congestion avoidance algorithm
based on data-center TCP congestion avoidance (DCTCP) to relay
information about the maximum queue depth that packets experienced to
the receiver. There's also a "nop" policy to disable congestion
avoidance for testing and benchmarking purposes.

The (initial) API for congestion avoidance policies is:

        void *   (* ctx_create)(void);

        void     (* ctx_destroy)(void * ctx);

These calls create / and or destroy a context for congestion control
for a specific flow. Thread-safety of the context is the
responsability of the flow allocator (operations on the ctx should be
performed under a lock).

        ca_wnd_t (* ctx_update_snd)(void * ctx,
                                    size_t len);

This is the sender call to update the context, and should be called
for every packet that is sent on the flow. The len parameter in this
API is the packet length, which allows calculating the bandwidth. It
returns an opaque union type that is used for the call to check/wait
if the congestion window is open or closed (and allowing to release
locks before waiting).

        bool     (* ctx_update_rcv)(void *     ctx,
                                    size_t     len,
                                    uint8_t    ecn,
                                    uint16_t * ece);

This is the call to update the flow congestion context on the receiver
side. It should be called for every received packet.  It gets the ecn
value from the packet and its length, and returns the ECE (explicit
congestion experienced) value to be sent to the sender in case of
congestion. The boolean returned signals whether or not a congestion
update needs to be sent.

        void     (* ctx_update_ece)(void *   ctx,
                                    uint16_t ece);

This is the call for the sending side top update the context when it
receives an ECE update from the receiver.

        void     (* wnd_wait)(ca_wnd_t wnd);

This is a (blocking) call that waits for the congestion window to
clear. It should be stateless (to avoid waiting under locks). This may
change later on if passing the context is needed for different algorithms.

        uint8_t  (* calc_ecn)(int    fd,
                              size_t len);

This is the call that intermediate IPCPs(routers) should use to update
the ECN field on passing packets.

The multi-bit ECN policy bases the value for the ECN field on the
depth of the rbuff queue packets will be sent on. I created another
call to grab the queue depth as fccntl is write-locking the
application. We can further optimize this to avoid most locking on the
rbuff.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 42 insertions, 27 deletions

diff --git a/src/tools/irm/irm_ipcp_bootstrap.c b/src/tools/irm/irm_ipcp_bootstrap.c
index 84b6759a..ba57a506 100644
--- a/src/tools/irm/irm_ipcp_bootstrap.c
+++ b/src/tools/irm/irm_ipcp_bootstrap.c
@@ -50,7 +50,7 @@
 #include <sys/socket.h>
 #endif
 
-#define UNICAST                 "unicast"
+#define UNICAST                "unicast"
 #define BROADCAST              "broadcast"
 #define UDP                    "udp"
 #define ETH_LLC                "eth-llc"
@@ -70,6 +70,7 @@
 #define DEFAULT_TTL            60
 #define DEFAULT_ADDR_AUTH      ADDR_AUTH_FLAT_RANDOM
 #define DEFAULT_ROUTING        ROUTING_LINK_STATE
+#define DEFAULT_CONG_AVOID     CA_MB_ECN
 #define DEFAULT_HASH_ALGO      DIR_HASH_SHA3_256
 #define DEFAULT_ETHERTYPE      0xA000
 #define DEFAULT_CLIENT_PORT    0x0000 /* random port */
@@ -79,6 +80,8 @@
 #define LINK_STATE_ROUTING     "link_state"
 #define LINK_STATE_LFA_ROUTING "lfa"
 #define LINK_STATE_ECM_ROUTING "ecmp"
+#define NONE_CA                "none"
+#define MB_ECN_CA              "mb-ecn"
 
 static void usage(void)
 {
@@ -95,11 +98,13 @@ static void usage(void)
                "                [ttl (max time-to-live value, default: %d)]\n"
                "                [addr_auth <ADDRESS_POLICY> (default: %s)]\n"
                "                [routing <ROUTING_POLICY> (default: %s)]\n"
+               "                [congestion <CONG_POLICY> (default: %s)]\n"
                "                [hash [ALGORITHM] (default: %s)]\n"
                "                [autobind]\n"
-               "where ADDRESS_POLICY = {"FLAT_RANDOM_ADDR_AUTH"}\n"
-               "      ROUTING_POLICY = {"LINK_STATE_ROUTING " "
+               "where ADDRESS_POLICY = {" FLAT_RANDOM_ADDR_AUTH "}\n"
+               "      ROUTING_POLICY = {" LINK_STATE_ROUTING " "
                LINK_STATE_LFA_ROUTING " " LINK_STATE_ECM_ROUTING "}\n"
+               "      CONG_POLICY = {" NONE_CA " " MB_ECN_CA "}\n"
                "      ALGORITHM = {" SHA3_224 " " SHA3_256 " "
                SHA3_384 " " SHA3_512 "}\n\n"
                "if TYPE == " UDP "\n"
@@ -130,7 +135,7 @@ static void usage(void)
                "if TYPE == " BROADCAST "\n"
                "                [autobind]\n\n",
                DEFAULT_ADDR_SIZE, DEFAULT_EID_SIZE, DEFAULT_TTL,
-               FLAT_RANDOM_ADDR_AUTH, LINK_STATE_ROUTING,
+               FLAT_RANDOM_ADDR_AUTH, LINK_STATE_ROUTING, MB_ECN_CA,
                SHA3_256, DEFAULT_SERVER_PORT, SHA3_256, 0xA000, SHA3_256,
                SHA3_256, SHA3_256);
 }
@@ -138,29 +143,30 @@ static void usage(void)
 int do_bootstrap_ipcp(int     argc,
                       char ** argv)
 {
-        char *             ipcp           = NULL;
-        pid_t              pid            = -1;
-        struct ipcp_config conf;
-        uint8_t            addr_size      = DEFAULT_ADDR_SIZE;
-        uint8_t            eid_size       = DEFAULT_EID_SIZE;
-        uint8_t            max_ttl        = DEFAULT_TTL;
-        enum pol_addr_auth addr_auth_type = DEFAULT_ADDR_AUTH;
-        enum pol_routing   routing_type   = DEFAULT_ROUTING;
-        enum pol_dir_hash  hash_algo      = DEFAULT_HASH_ALGO;
-        uint32_t           ip_addr        = 0;
-        uint32_t           dns_addr       = DEFAULT_DDNS;
-        char *             ipcp_type      = NULL;
-        enum ipcp_type     type           = IPCP_INVALID;
-        char *             layer          = NULL;
-        char *             dev            = NULL;
-        uint16_t           ethertype      = DEFAULT_ETHERTYPE;
-        struct ipcp_info * ipcps;
-        ssize_t            len            = 0;
-        int                i              = 0;
-        bool               autobind       = false;
-        int                cargs;
-        int                cport          = DEFAULT_CLIENT_PORT;
-        int                sport          = DEFAULT_SERVER_PORT;
+        char *              ipcp           = NULL;
+        pid_t               pid            = -1;
+        struct ipcp_config  conf;
+        uint8_t             addr_size      = DEFAULT_ADDR_SIZE;
+        uint8_t             eid_size       = DEFAULT_EID_SIZE;
+        uint8_t             max_ttl        = DEFAULT_TTL;
+        enum pol_addr_auth  addr_auth_type = DEFAULT_ADDR_AUTH;
+        enum pol_routing    routing_type   = DEFAULT_ROUTING;
+        enum pol_dir_hash   hash_algo      = DEFAULT_HASH_ALGO;
+        enum pol_cong_avoid cong_avoid     = DEFAULT_CONG_AVOID;
+        uint32_t            ip_addr        = 0;
+        uint32_t            dns_addr       = DEFAULT_DDNS;
+        char *              ipcp_type      = NULL;
+        enum ipcp_type      type           = IPCP_INVALID;
+        char *              layer          = NULL;
+        char *              dev            = NULL;
+        uint16_t            ethertype      = DEFAULT_ETHERTYPE;
+        struct ipcp_info *  ipcps;
+        ssize_t             len            = 0;
+        int                 i              = 0;
+        bool                autobind       = false;
+        int                 cargs;
+        int                 cport          = DEFAULT_CLIENT_PORT;
+        int                 sport          = DEFAULT_SERVER_PORT;
 
         while (argc > 0) {
                 cargs = 2;
@@ -230,6 +236,14 @@ int do_bootstrap_ipcp(int     argc,
                                 routing_type = ROUTING_LINK_STATE_ECMP;
                         else
                                 goto unknown_param;
+                } else if (matches(*argv, "congestion") == 0) {
+                        if (strcmp(NONE_CA, *(argv + 1)) == 0)
+                                cong_avoid = CA_NONE;
+                        else if (strcmp(MB_ECN_CA,
+                                        *(argv + 1)) == 0)
+                                cong_avoid = CA_MB_ECN;
+                        else
+                                goto unknown_param;
                 } else {
                         printf("Unknown option: \"%s\".\n", *argv);
                         return -1;
@@ -315,6 +329,7 @@ int do_bootstrap_ipcp(int     argc,
                                 conf.max_ttl        = max_ttl;
                                 conf.addr_auth_type = addr_auth_type;
                                 conf.routing_type   = routing_type;
+                                conf.cong_avoid     = cong_avoid;
                                 break;
                         case IPCP_UDP:
                                 if (ip_addr == 0)