- 

From 4021058d729fd618e5770300664ecfcc6fd29d5d Mon Sep 17 00:00:00 2001

From: Chris Rorvick <chris@rorvick.com>

Date: Tue, 28 May 2019 00:44:52 -0500

Subject: [PATCH] prefer routable IPv6 addresses over link-local

Currently the IPv6 address provided for an interface in the $(sys.inet6)

data is arbitrary if more than one address is bound to that interface.

Given that IPv6 requires all interfaces have a link-local address, this

is a common scenario.  Add a mechanism to GetProcFileInfo() to choose

between the previous and new entries if more than one is found for an

extracted key, and use this mechanism to rank link-local addresses below

others.

Also, the post-processing functions passed to GetProcFileInfo() have a

strange return value.  This is seemingly due to a misunderstanding with

how function pointer types relate to function definitions.  Clean this

up.

---

 libenv/unix_iface.c | 106 +++++++++++++++++++++++++++++++++++---------

 1 file changed, 86 insertions(+), 20 deletions(-)

diff --git a/libenv/unix_iface.c b/libenv/unix_iface.c

index c62e1cb73..0adbb0a7b 100644

--- a/libenv/unix_iface.c

+++ b/libenv/unix_iface.c

@@ -88,6 +88,7 @@ static void InitIgnoreInterfaces(void);

 static Rlist *IGNORE_INTERFACES = NULL; /* GLOBAL_E */

 typedef void (*ProcPostProcessFn)(void *ctx, void *json);

+typedef JsonElement * (*ProcTiebreakerFn)(JsonElement *prev_item, JsonElement *this_item);

 /*********************************************************************/

@@ -1021,7 +1022,7 @@ static void NetworkingRoutesPostProcessInfo(

 # endif

 }

-static ProcPostProcessFn NetworkingIPv6RoutesPostProcessInfo(

+static void NetworkingIPv6RoutesPostProcessInfo(

     ARG_UNUSED void *passed_ctx, ARG_LINUX_ONLY void *json)

 {

 # if defined (__linux__)

@@ -1054,10 +1055,9 @@ static ProcPostProcessFn NetworkingIPv6RoutesPostProcessInfo(

     // like we do with IPv4 routes

 # endif

-    return NULL;

 }

-static ProcPostProcessFn NetworkingIPv6AddressesPostProcessInfo(ARG_UNUSED void *passed_ctx, void *json)

+static void NetworkingIPv6AddressesPostProcessInfo(ARG_UNUSED void *passed_ctx, void *json)

 {

     JsonElement *entry = json;

@@ -1066,7 +1066,50 @@ static ProcPostProcessFn NetworkingIPv6AddressesPostProcessInfo(ARG_UNUSED void

     JsonExtractParsedNumber(entry, "raw_device_number", "device_number", true, false);

     JsonExtractParsedNumber(entry, "raw_prefix_length", "prefix_length", true, false);

     JsonExtractParsedNumber(entry, "raw_scope", "scope", true, false);

-    return NULL;

+}

+

+static unsigned RankIPv6Address(const char *address)

+{

+    unsigned long first_word = 0;

+    char *end;

+

+    if (address == NULL)

+    {

+        return 0;

+    }

+

+    first_word = strtoul(address, &end, 16);

+

+    if (*end != ':')

+    {

+        return 0;  // invalid IPv6 address?

+    }

+

+    if ((first_word & 0xffc0) == 0xfe80)

+    {

+        // link-local (fe80:://10)

+

+        return 1;

+    }

+    else

+    {

+        return 2;

+    }

+}

+

+static JsonElement *NetworkingIPv6AddressesTiebreaker(JsonElement *prev_item, JsonElement *this_item)

+{

+    const char *prev_addr = JsonObjectGetAsString(prev_item, "address");

+    const char *this_addr = JsonObjectGetAsString(this_item, "address");

+

+    if (RankIPv6Address(this_addr) >= RankIPv6Address(prev_addr))

+    {

+        return this_item;

+    }

+    else

+    {

+        return prev_item;

+    }

 }

 /*******************************************************************/

@@ -1095,7 +1138,7 @@ static const char* GetPortStateString(ARG_LINUX_ONLY int state)

 // used in evalfunction.c but defined here so

 // JsonRewriteParsedIPAddress() etc. can stay local

-ProcPostProcessFn NetworkingPortsPostProcessInfo(ARG_UNUSED void *passed_ctx, void *json)

+void NetworkingPortsPostProcessInfo(ARG_UNUSED void *passed_ctx, void *json)

 {

     JsonElement *conn = json;

@@ -1112,8 +1155,6 @@ ProcPostProcessFn NetworkingPortsPostProcessInfo(ARG_UNUSED void *passed_ctx, vo

             JsonObjectAppendString(conn, "state", GetPortStateString(num_state));

         }

     }

-

-    return NULL;

 }

 /*******************************************************************/

@@ -1180,7 +1221,7 @@ static JsonElement* GetNetworkingStatsInfo(const char *filename)

 // always returns the parsed data. If the key is not NULL, also

 // creates a sys.KEY variable.

-JsonElement* GetProcFileInfo(EvalContext *ctx, const char* filename, const char* key, const char* extracted_key, ProcPostProcessFn post, const char* regex)

+JsonElement* GetProcFileInfo(EvalContext *ctx, const char* filename, const char* key, const char* extracted_key, ProcPostProcessFn post, ProcTiebreakerFn tiebreak, const char* regex)

 {

     JsonElement *info = NULL;

     bool extract_key_mode = (extracted_key != NULL);

@@ -1218,14 +1259,39 @@ JsonElement* GetProcFileInfo(EvalContext *ctx, const char* filename, const char*

                     if (extract_key_mode)

                     {

-                        if (JsonObjectGetAsString(item, extracted_key) == NULL)

+                        const char *extracted_key_value = JsonObjectGetAsString(item, extracted_key);

+

+                        if (extracted_key_value == NULL)

                         {

                             Log(LOG_LEVEL_ERR, "While parsing %s, looked to extract key %s but couldn't find it in line %s", filename, extracted_key, line);

                         }

                         else

                         {

-                            Log(LOG_LEVEL_DEBUG, "While parsing %s, got key %s from line %s", filename, JsonObjectGetAsString(item, extracted_key), line);

-                            JsonObjectAppendElement(info, JsonObjectGetAsString(item, extracted_key), item);

+                            JsonElement *prev_item = JsonObjectGet(info, extracted_key_value);

+

+                            Log(LOG_LEVEL_DEBUG, "While parsing %s, got key %s from line %s", filename, extracted_key_value, line);

+

+                            if (prev_item != NULL && tiebreak != NULL)

+                            {

+                                JsonElement *winner = (*tiebreak)(prev_item, item);

+

+                                if (winner == prev_item)

+                                {

+                                    Log(LOG_LEVEL_DEBUG, "Multiple entries for key %s, preferring previous value", extracted_key_value);

+

+                                    JsonDestroy(item);

+                                    item = NULL;

+                                }

+                                else

+                                {

+                                    Log(LOG_LEVEL_DEBUG, "Multiple entries for key %s, preferring new value", extracted_key_value);

+                                }

+                            }

+

+                            if (item != NULL)

+                            {

+                                JsonObjectAppendElement(info, extracted_key_value, item);

+                            }

                         }

                     }

                     else

@@ -1274,7 +1340,7 @@ void GetNetworkingInfo(EvalContext *ctx)

     }

     BufferPrintf(pbuf, "%s/proc/net/route", procdir_root);

-    JsonElement *routes = GetProcFileInfo(ctx, BufferData(pbuf),  NULL, NULL, (ProcPostProcessFn) &NetworkingRoutesPostProcessInfo,

+    JsonElement *routes = GetProcFileInfo(ctx, BufferData(pbuf),  NULL, NULL, &NetworkingRoutesPostProcessInfo, NULL,

                     // format: Iface	Destination	Gateway 	Flags	RefCnt	Use	Metric	Mask		MTU	Window	IRTT

                     //         eth0	00000000	0102A8C0	0003	0	0	1024	00000000	0	0	0

                     "^(?<interface>\\S+)\\t(?<raw_dest>[[:xdigit:]]+)\\t(?<raw_gw>[[:xdigit:]]+)\\t(?<raw_flags>[[:xdigit:]]+)\\t(?<refcnt>\\d+)\\t(?<use>\\d+)\\t(?<metric>[[:xdigit:]]+)\\t(?<raw_mask>[[:xdigit:]]+)\\t(?<mtu>\\d+)\\t(?<window>\\d+)\\t(?<irtt>[[:xdigit:]]+)");

@@ -1322,7 +1388,7 @@ void GetNetworkingInfo(EvalContext *ctx)

     JsonElement *inet6 = JsonObjectCreate(3);

     BufferPrintf(pbuf, "%s/proc/net/snmp6", procdir_root);

-    JsonElement *inet6_stats = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, NULL,

+    JsonElement *inet6_stats = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, NULL, NULL,

                                                "^\\s*(?<key>\\S+)\\s+(?<value>\\d+)");

     if (inet6_stats != NULL)

@@ -1348,7 +1414,7 @@ void GetNetworkingInfo(EvalContext *ctx)

     }

     BufferPrintf(pbuf, "%s/proc/net/ipv6_route", procdir_root);

-    JsonElement *inet6_routes = GetProcFileInfo(ctx, BufferData(pbuf),  NULL, NULL, (ProcPostProcessFn) &NetworkingIPv6RoutesPostProcessInfo,

+    JsonElement *inet6_routes = GetProcFileInfo(ctx, BufferData(pbuf),  NULL, NULL, &NetworkingIPv6RoutesPostProcessInfo, NULL,

                     // format: dest                    dest_prefix source                source_prefix next_hop                         metric   refcnt   use      flags        interface

                     //         fe800000000000000000000000000000 40 00000000000000000000000000000000 00 00000000000000000000000000000000 00000100 00000000 00000000 00000001     eth0

                     "^(?<raw_dest>[[:xdigit:]]+)\\s+(?<dest_prefix>[[:xdigit:]]+)\\s+"

@@ -1363,7 +1429,7 @@ void GetNetworkingInfo(EvalContext *ctx)

     }

     BufferPrintf(pbuf, "%s/proc/net/if_inet6", procdir_root);

-    JsonElement *inet6_addresses = GetProcFileInfo(ctx, BufferData(pbuf),  NULL, "interface", (ProcPostProcessFn) &NetworkingIPv6AddressesPostProcessInfo,

+    JsonElement *inet6_addresses = GetProcFileInfo(ctx, BufferData(pbuf),  NULL, "interface", &NetworkingIPv6AddressesPostProcessInfo, &NetworkingIPv6AddressesTiebreaker,

                     // format: address device_number prefix_length scope flags interface_name

                     // 00000000000000000000000000000001 01 80 10 80       lo

                     // fe80000000000000004249fffebdd7b4 04 40 20 80  docker0

@@ -1387,7 +1453,7 @@ void GetNetworkingInfo(EvalContext *ctx)

     BufferPrintf(pbuf, "%s/proc/net/dev", procdir_root);

     JsonElement *interfaces_data =

-    GetProcFileInfo(ctx, BufferData(pbuf), "interfaces_data", "device", NULL,

+    GetProcFileInfo(ctx, BufferData(pbuf), "interfaces_data", "device", NULL, NULL,

                     "^\\s*(?<device>[^:]+)\\s*:\\s*"

                     // All of the below are just decimal digits separated by spaces

                     "(?<receive_bytes>\\d+)\\s+"

@@ -1420,28 +1486,28 @@ JsonElement* GetNetworkingConnections(EvalContext *ctx)

     Buffer *pbuf = BufferNew();

     BufferPrintf(pbuf, "%s/proc/net/tcp", procdir_root);

-    data = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, (ProcPostProcessFn) &NetworkingPortsPostProcessInfo, ports_regex);

+    data = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, &NetworkingPortsPostProcessInfo, NULL, ports_regex);

     if (data != NULL)

     {

         JsonObjectAppendElement(json, "tcp", data);

     }

     BufferPrintf(pbuf, "%s/proc/net/tcp6", procdir_root);

-    data = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, (ProcPostProcessFn) &NetworkingPortsPostProcessInfo, ports_regex);

+    data = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, &NetworkingPortsPostProcessInfo, NULL, ports_regex);

     if (data != NULL)

     {

         JsonObjectAppendElement(json, "tcp6", data);

     }

     BufferPrintf(pbuf, "%s/proc/net/udp", procdir_root);

-    data = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, (ProcPostProcessFn) &NetworkingPortsPostProcessInfo, ports_regex);

+    data = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, &NetworkingPortsPostProcessInfo, NULL, ports_regex);

     if (data != NULL)

     {

         JsonObjectAppendElement(json, "udp", data);

     }

     BufferPrintf(pbuf, "%s/proc/net/udp6", procdir_root);

-    data = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, (ProcPostProcessFn) &NetworkingPortsPostProcessInfo, ports_regex);

+    data = GetProcFileInfo(ctx, BufferData(pbuf), NULL, NULL, &NetworkingPortsPostProcessInfo, NULL, ports_regex);

     if (data != NULL)

     {

         JsonObjectAppendElement(json, "udp6", data);

-- 

2.24.1