DTrace probes: support X-Forwarded-For

INTRO-385

1 files changed, 78 insertions, 12 deletions

diff --git a/src/node.d b/src/node.d
index b81930c813..c666127fff 100644
--- a/src/node.d
+++ b/src/node.d
@@ -65,29 +65,95 @@ translator node_connection_t <node_dtrace_connection_t *nc> {
 };
 
 typedef struct {
+	uint32_t version;
+} node_dtrace_http_request_t;
+
+typedef struct {
 	uint32_t url;
 	uint32_t method;
-} node_dtrace_http_request_t;
+} node_dtrace_http_request_v0_t;
+
+typedef struct {
+	uint32_t version;
+	uint32_t url;
+	uint32_t method;
+	uint32_t forwardedFor;
+} node_dtrace_http_request_v1_t;
 
 typedef struct {
 	uint64_t url;
 	uint64_t method;
-} node_dtrace_http_request64_t;
+} node_dtrace_http_request64_v0_t;
+
+typedef struct {
+	uint32_t version;
+	uint32_t pad;
+	uint64_t url;
+	uint64_t method;
+	uint64_t forwardedFor;
+} node_dtrace_http_request64_v1_t;
 
 typedef struct {
 	string url;
 	string method;
+	string forwardedFor;
 } node_http_request_t;
 
+/*
+ * This translator is even filthier than usual owing to our attempts to
+ * maintain backwards compatibility.  Previous versions of node used an
+ * http_request struct that had fields for "url" and "method".  The current
+ * version also provides a "forwardedFor" field.  To distinguish the binary
+ * representations of these structs, the new version also prepends a "version"
+ * member (where the old one has a "url" pointer).  So each field that we're
+ * translating below first switches on the value of this "version" field: if
+ * it's larger than 4096, we know we must be looking at the "url" pointer of
+ * the older structure version.  Otherwise, we must be looking at the new
+ * version.  Besides this, we have the usual switch based on the userland
+ * process data model.  This would all be simpler with macros, but those aren't
+ * available in delivered D library files since that would make DTrace
+ * dependent on cpp, which isn't always available.
+ */
 translator node_http_request_t <node_dtrace_http_request_t *nd> {
-	url = curpsinfo->pr_dmodel == PR_MODEL_ILP32 ?
-	    copyinstr((uintptr_t)*(uint32_t *)copyin((uintptr_t)&nd->url,
-	    sizeof (int32_t))) :
-	    copyinstr((uintptr_t)*(uint64_t *)copyin((uintptr_t)
-	    &((node_dtrace_http_request64_t *)nd)->url, sizeof (int64_t)));
-	method = curpsinfo->pr_dmodel == PR_MODEL_ILP32 ?
-	    copyinstr((uintptr_t)*(uint32_t *)copyin((uintptr_t)&nd->method,
-	    sizeof (int32_t))) :
-	    copyinstr((uintptr_t)*(uint64_t *)copyin((uintptr_t)
-	    &((node_dtrace_http_request64_t *)nd)->method, sizeof (int64_t)));
+	url = (*(uint32_t *)copyin((uintptr_t)&nd->version, sizeof (uint32_t))) >= 4096 ?
+	    (curpsinfo->pr_dmodel == PR_MODEL_ILP32 ?
+		copyinstr(*(uint32_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request_v0_t *)nd)->url,
+		    sizeof (uint32_t))) :
+		copyinstr(*(uint64_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request64_v0_t *)nd)->url,
+		    sizeof (uint64_t)))) :
+	    (curpsinfo->pr_dmodel == PR_MODEL_ILP32 ?
+		copyinstr(*(uint32_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request_v1_t *)nd)->url,
+		    sizeof (uint32_t))) :
+		copyinstr(*(uint64_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request64_v1_t *)nd)->url,
+		    sizeof (uint64_t))));
+
+	method = (*(uint32_t *)copyin((uintptr_t)&nd->version, sizeof (uint32_t))) >= 4096 ?
+	    (curpsinfo->pr_dmodel == PR_MODEL_ILP32 ?
+		copyinstr(*(uint32_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request_v0_t *)nd)->method,
+		    sizeof (uint32_t))) :
+		copyinstr(*(uint64_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request64_v0_t *)nd)->method,
+		    sizeof (uint64_t)))) :
+	    (curpsinfo->pr_dmodel == PR_MODEL_ILP32 ?
+		copyinstr(*(uint32_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request_v1_t *)nd)->method,
+		    sizeof (uint32_t))) :
+		copyinstr(*(uint64_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request64_v1_t *)nd)->method,
+		    sizeof (uint64_t))));
+	
+	forwardedFor = (*(uint32_t *)
+	    copyin((uintptr_t)&nd->version, sizeof (uint32_t))) >= 4096 ? "" :
+	    (curpsinfo->pr_dmodel == PR_MODEL_ILP32 ?
+		copyinstr(*(uint32_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request_v1_t *)nd)->forwardedFor,
+		    sizeof (uint32_t))) :
+		copyinstr(*(uint64_t *)copyin((uintptr_t)
+		    &((node_dtrace_http_request64_v1_t *)nd)->forwardedFor,
+		    sizeof (uint64_t))));
 };