[USM] Introduce tail cals for the Postgres monitoring

pkg/network/ebpf/c/protocols/classification/defs.h

@@ -152,6 +152,7 @@ typedef enum {
     PROG_KAFKA_TERMINATION,
     PROG_GRPC,
     PROG_POSTGRES,
+    PROG_POSTGRES_HANDLE_RESPONSE,
     PROG_POSTGRES_PROCESS_PARSE_MESSAGE,
     PROG_POSTGRES_TERMINATION,
     PROG_REDIS,

pkg/network/ebpf/c/protocols/postgres/decoding-maps.h

@@ -12,4 +12,7 @@ BPF_HASH_MAP(postgres_in_flight, conn_tuple_t, postgres_transaction_t, 0)
 // Acts as a scratch buffer for Postgres events, for preparing events before they are sent to userspace.
 BPF_PERCPU_ARRAY_MAP(postgres_scratch_buffer, postgres_event_t, 1)
 
+// Maintains the current state of tail calls for each Postgres message.
+BPF_PERCPU_ARRAY_MAP(postgres_iterations, postgres_tail_call_state_t, 1)
+
 #endif

pkg/network/ebpf/c/protocols/postgres/decoding.h

@@ -65,6 +65,7 @@ static __always_inline void handle_command_complete(conn_tuple_t *conn_tuple, po
     bpf_map_delete_elem(&postgres_in_flight, conn_tuple);
 }
 
+// Handles a TCP termination event by deleting the connection tuple from the in-flight map.
 static void __always_inline postgres_tcp_termination(conn_tuple_t *tup) {
     bpf_map_delete_elem(&postgres_in_flight, tup);
     flip_tuple(tup);
@@ -107,12 +108,28 @@ static int __always_inline skip_string(pktbuf_t pkt, int message_len) {
     return SKIP_STRING_FAILED;
 }
 
-// Main processing logic for the Postgres protocol. It reads the first message header and decides what to do based on the
-// message tag. If the message is a new query, it stores the query in the in-flight map. If the message is a command
-// complete, it enqueues the transaction and deletes it from the in-flight map. If the message is not a command complete,
-// it tries to read up to POSTGRES_MAX_MESSAGES messages, looking for a command complete message.
-// If the message is not a new query or a command complete, it ignores the message.
-static __always_inline void postgres_entrypoint(pktbuf_t pkt, conn_tuple_t *conn_tuple, struct pg_message_header *header, __u8 tags) {
+// Reads the first message header and decides what to do based on the
+// message tag. If the message is a new query, it stores the query in the in-flight map.
+// If the message is a parse message, we tail call to the dedicated process_parse_message program.
+// If the message is a command complete, it calls the handle_command_complete program.
+static __always_inline void postgres_handle_message(pktbuf_t pkt, conn_tuple_t *conn_tuple, struct pg_message_header *header, __u8 tags) {
+    // If the message is a parse message, we tail call to the dedicated function to handle it as it is too large to be
+    // inlined in the main function.
+    if (header->message_tag == POSTGRES_PARSE_MAGIC_BYTE) {
+        pktbuf_tail_call_option_t process_parse_tail_call_array[] = {
+            [PKTBUF_SKB] = {
+                .prog_array_map = &protocols_progs,
+                .index = PROG_POSTGRES_PROCESS_PARSE_MESSAGE,
+            },
+            [PKTBUF_TLS] = {
+                .prog_array_map = &tls_process_progs,
+                .index = PROG_POSTGRES_PROCESS_PARSE_MESSAGE,
+            },
+        };
+        pktbuf_tail_call_compact(pkt, process_parse_tail_call_array);
+        return;
+    }
+
     // If the message is a new query, we store the query in the in-flight map.
     // If we had a transaction for the connection, we override it and drops the previous one.
     if (header->message_tag == POSTGRES_QUERY_MAGIC_BYTE) {
@@ -125,27 +142,25 @@ static __always_inline void postgres_entrypoint(pktbuf_t pkt, conn_tuple_t *conn
         return;
     }
 
-    // We didn't find a new query, thus we assume we're in the middle of a transaction.
-    // We look up the transaction in the in-flight map, and if it doesn't exist, we ignore the message.
-    postgres_transaction_t *transaction = bpf_map_lookup_elem(&postgres_in_flight, conn_tuple);
-    if (!transaction) {
+    const __u32 zero = 0;
+    postgres_tail_call_state_t *iteration_value = bpf_map_lookup_elem(&postgres_iterations, &zero);
+    if (iteration_value == NULL) {
         return;
     }
 
-#pragma unroll(POSTGRES_MAX_MESSAGES)
-    for (__u32 iteration = 0; iteration < POSTGRES_MAX_MESSAGES; ++iteration) {
-        if (!read_message_header(pkt, header)) {
-            break;
-        }
-        if (header->message_tag == POSTGRES_COMMAND_COMPLETE_MAGIC_BYTE) {
-            handle_command_complete(conn_tuple, transaction);
-            break;
-        }
-        // We didn't find a command complete message, so we advance the data offset to the end of the message.
-        // reminder, the message length includes the size of the payload, 4 bytes of the message length itself, but not
-        // the message tag. So we need to add 1 to the message length to jump over the entire message.
-        pktbuf_advance(pkt, header->message_len + 1);
-    }
+    iteration_value->iteration = 0;
+    iteration_value->data_off = 0;
+    pktbuf_tail_call_option_t handle_response_tail_call_array[] = {
+        [PKTBUF_SKB] = {
+            .prog_array_map = &protocols_progs,
+            .index = PROG_POSTGRES_HANDLE_RESPONSE,
+        },
+        [PKTBUF_TLS] = {
+            .prog_array_map = &tls_process_progs,
+            .index = PROG_POSTGRES_HANDLE_RESPONSE,
+        },
+    };
+    pktbuf_tail_call_compact(pkt, handle_response_tail_call_array);
     return;
 }
 
@@ -180,12 +195,77 @@ static __always_inline void postgres_handle_parse_message(pktbuf_t pkt, conn_tup
     return;
 }
 
+// Handles Postgres command complete messages by examining packet data for both plaintext and TLS traffic.
+// This function handles multiple messages within a single packet, processing up to POSTGRES_MAX_MESSAGES_PER_TAIL_CALL
+// messages per call. When more messages exist beyond this limit, it uses tail call chaining (up to
+// POSTGRES_MAX_TAIL_CALLS_FOR_MAX_MESSAGES) to continue processing.
+static __always_inline bool handle_response(pktbuf_t pkt, conn_tuple_t conn_tuple) {
+    const __u32 zero = 0;
+    bool found_command_complete = false;
+    struct pg_message_header header;
+
+    postgres_tail_call_state_t *iteration_value = bpf_map_lookup_elem(&postgres_iterations, &zero);
+    if (iteration_value == NULL) {
+        bpf_map_delete_elem(&postgres_in_flight, &conn_tuple);
+        return 0;
+    }
+
+    if (iteration_value->iteration >= POSTGRES_MAX_TAIL_CALLS_FOR_MAX_MESSAGES) {
+        return 0;
+    }
+
+    if (iteration_value->data_off != 0) {
+        pktbuf_set_offset(pkt, iteration_value->data_off);
+    }
+
+    // We didn't find a new query, thus we assume we're in the middle of a transaction.
+    // We look up the transaction in the in-flight map, and if it doesn't exist, we ignore the message.
+    postgres_transaction_t *transaction = bpf_map_lookup_elem(&postgres_in_flight, &conn_tuple);
+    if (!transaction) {
+        return 0;
+    }
+
+#pragma unroll(POSTGRES_MAX_MESSAGES_PER_TAIL_CALL)
+    for (__u32 iteration = 0; iteration < POSTGRES_MAX_MESSAGES_PER_TAIL_CALL; ++iteration) {
+        if (!read_message_header(pkt, &header)) {
+            break;
+        }
+        if (header.message_tag == POSTGRES_COMMAND_COMPLETE_MAGIC_BYTE) {
+            handle_command_complete(&conn_tuple, transaction);
+            found_command_complete = true;
+            break;
+        }
+        // We didn't find a command complete message, so we advance the data offset to the end of the message.
+        // reminder, the message length includes the size of the payload, 4 bytes of the message length itself, but not
+        // the message tag. So we need to add 1 to the message length to jump over the entire message.
+        pktbuf_advance(pkt, header.message_len + 1);
+    }
+
+    if (found_command_complete) {
+        return 0;
+    }
+    // We didn't find a command complete message, so we need to continue processing the packet.
+    // We save the current data offset and increment the iteration counter.
+    iteration_value->iteration += 1;
+    iteration_value->data_off = pktbuf_data_offset(pkt);
+    pktbuf_tail_call_option_t handle_response_tail_call_array[] = {
+        [PKTBUF_SKB] = {
+            .prog_array_map = &protocols_progs,
+            .index = PROG_POSTGRES_HANDLE_RESPONSE,
+        },
+        [PKTBUF_TLS] = {
+            .prog_array_map = &tls_process_progs,
+            .index = PROG_POSTGRES_HANDLE_RESPONSE,
+        },
+    };
+    pktbuf_tail_call_compact(pkt, handle_response_tail_call_array);
+    return 0;
+}
+
 // Entrypoint to process plaintext Postgres traffic. Pulls the connection tuple and the packet buffer from the map and
 // calls the main processing function. If the packet is a TCP termination, it calls the termination function.
-// If the message is a parse message, it tail calls to the dedicated function to handle it as it is too large to be
-// inlined in the main entrypoint. Otherwise, it calls the main processing function.
-SEC("socket/postgres_process")
-int socket__postgres_process(struct __sk_buff* skb) {
+SEC("socket/postgres_handle")
+int socket__postgres_handle(struct __sk_buff* skb) {
     skb_info_t skb_info = {};
     conn_tuple_t conn_tuple = {};
 
@@ -206,13 +286,30 @@ int socket__postgres_process(struct __sk_buff* skb) {
         return 0;
     }
 
-    // If the message is a parse message, we tail call to the dedicated function to handle it.
-    if (header.message_tag == POSTGRES_PARSE_MAGIC_BYTE) {
-        bpf_tail_call_compat(skb, &protocols_progs, PROG_POSTGRES_PROCESS_PARSE_MESSAGE);
+    postgres_handle_message(pkt, &conn_tuple, &header, NO_TAGS);
+    return 0;
+}
+
+// Handles plain text command complete messages for plaintext Postgres traffic. Pulls the connection tuple and the
+// packet buffer from the map and calls the dedicated function to handle the message.
+SEC("socket/postgres_handle_response")
+int socket__postgres_handle_response(struct __sk_buff* skb) {
+    skb_info_t skb_info = {};
+    conn_tuple_t conn_tuple = {};
+
+    if (!fetch_dispatching_arguments(&conn_tuple, &skb_info)) {
+        return 0;
+    }
+
+    if (is_tcp_termination(&skb_info)) {
+        postgres_tcp_termination(&conn_tuple);
         return 0;
     }
 
-    postgres_entrypoint(pkt, &conn_tuple, &header, NO_TAGS);
+    normalize_tuple(&conn_tuple);
+
+    pktbuf_t pkt = pktbuf_from_skb(skb, &skb_info);
+    handle_response(pkt, conn_tuple);
     return 0;
 }
 
@@ -235,10 +332,9 @@ int socket__postgres_process_parse_message(struct __sk_buff* skb) {
 }
 
 // Entrypoint to process TLS Postgres traffic. Pulls the connection tuple and the packet buffer from the map and calls
-// the main processing function. If the packet is a Parse message, it tail calls to the dedicated function to handle it.
-// Otherwise, it calls the main processing function.
-SEC("uprobe/postgres_tls_process")
-int uprobe__postgres_tls_process(struct pt_regs *ctx) {
+// the main processing function.
+SEC("uprobe/postgres_tls_handle")
+int uprobe__postgres_tls_handle(struct pt_regs *ctx) {
     const __u32 zero = 0;
 
     tls_dispatcher_arguments_t *args = bpf_map_lookup_elem(&tls_dispatcher_arguments, &zero);
@@ -255,12 +351,7 @@ int uprobe__postgres_tls_process(struct pt_regs *ctx) {
         return 0;
     }
 
-    // If the message is a parse message, we tail call to the dedicated function to handle it.
-    if (header.message_tag == POSTGRES_PARSE_MAGIC_BYTE) {
-        bpf_tail_call_compat(ctx, &tls_process_progs, PROG_POSTGRES_PROCESS_PARSE_MESSAGE);
-        return 0;
-    }
-    postgres_entrypoint(pkt, &tup, &header, (__u8)args->tags);
+    postgres_handle_message(pkt, &tup, &header, (__u8)args->tags);
     return 0;
 }
 
@@ -299,4 +390,21 @@ int uprobe__postgres_tls_termination(struct pt_regs *ctx) {
     return 0;
 }
 
+// Handles message parsing for a TLS Postgres traffic.
+SEC("uprobe/postgres_tls_handle_response")
+int uprobe__postgres_tls_handle_response(struct pt_regs *ctx) {
+    const __u32 zero = 0;
+
+    tls_dispatcher_arguments_t *args = bpf_map_lookup_elem(&tls_dispatcher_arguments, &zero);
+    if (args == NULL) {
+        return 0;
+    }
+
+    // Copying the tuple to the stack to handle verifier issues on kernel 4.14.
+    conn_tuple_t tup = args->tup;
+    pktbuf_t pkt = pktbuf_from_tls(ctx, args);
+    handle_response(pkt, tup);
+    return 0;
+}
+
 #endif

pkg/network/ebpf/c/protocols/postgres/types.h

@@ -6,8 +6,11 @@
 // Maximum length of Postgres query to send to userspace.
 #define POSTGRES_BUFFER_SIZE 160
 
-// Maximum number of Postgres messages we can parse for a single packet.
-#define POSTGRES_MAX_MESSAGES 80
+// Represents the maximum number of tail calls we can use to process a single message.
+#define POSTGRES_MAX_TAIL_CALLS_FOR_MAX_MESSAGES 1
+
+// Represents the maximum number of messages we process in a single tail call.
+#define POSTGRES_MAX_MESSAGES_PER_TAIL_CALL 80
 
 // Postgres transaction information we store in the kernel.
 typedef struct {
@@ -26,4 +29,11 @@ typedef struct {
     postgres_transaction_t tx;
 } postgres_event_t;
 
+typedef struct {
+    __u8 iteration;
+    // Saving the packet data offset is crucial for maintaining the current read position and ensuring proper utilization
+    // of tail calls.
+    __u32 data_off;
+} postgres_tail_call_state_t;
+
 #endif

pkg/network/protocols/ebpf_types.go

@@ -9,6 +9,7 @@ package protocols
 
 // #cgo CFLAGS: -I ../../ebpf/c  -I ../ebpf/c
 // #include "../ebpf/c/protocols/classification/defs.h"
+// #include "../ebpf/c/protocols/postgres/types.h"
 import "C"
 
 const (
@@ -17,6 +18,13 @@ const (
 	layerEncryptionBit  = C.LAYER_ENCRYPTION_BIT
 )
 
+const (
+	// PostgresMaxMessagesPerTailCall is the maximum number of messages that can be processed in a single tail call in our Postgres decoding solution
+	PostgresMaxMessagesPerTailCall = C.POSTGRES_MAX_MESSAGES_PER_TAIL_CALL
+	// PostgresMaxTailCalls is the maximum number of tail calls that can be made in our Postgres decoding solution
+	PostgresMaxTailCalls = C.POSTGRES_MAX_TAIL_CALLS_FOR_MAX_MESSAGES
+)
+
 // DispatcherProgramType is a C type to represent the eBPF programs used for tail calls.
 type DispatcherProgramType C.dispatcher_prog_t
 
@@ -63,6 +71,8 @@ const (
 	ProgramKafkaTermination ProgramType = C.PROG_KAFKA_TERMINATION
 	// ProgramPostgres is the Golang representation of the C.PROG_POSTGRES enum
 	ProgramPostgres ProgramType = C.PROG_POSTGRES
+	// ProgramPostgresHandleResponse is the Golang representation of the C.PROG_POSTGRES_HANDLE_RESPONSE enum
+	ProgramPostgresHandleResponse ProgramType = C.PROG_POSTGRES_HANDLE_RESPONSE
 	// ProgramPostgresParseMessage is the Golang representation of the C.PROG_POSTGRES_PROCESS_PARSE_MESSAGE enum
 	ProgramPostgresParseMessage ProgramType = C.PROG_POSTGRES_PROCESS_PARSE_MESSAGE
 	// ProgramPostgresTermination is tail call to process Postgres termination.