decode/tcp: reduce size needed for SACK tracking

No longer use a pointer, but rather an offset.

Part of effort to make Packet more compact.

Ticket: #6938.

src/decode-tcp.c

@@ -149,10 +149,14 @@ static void DecodeTCPOptions(Packet *p, const uint8_t *pkt, uint16_t pktlen)
                     {
                         ENGINE_SET_EVENT(p,TCP_OPT_INVALID_LEN);
                     } else {
-                        if (p->tcpvars.sack.type != 0) {
+                        if (p->tcpvars.sack_set) {
                             ENGINE_SET_EVENT(p,TCP_OPT_DUPLICATE);
                         } else {
-                            SET_OPTS(p->tcpvars.sack, tcp_opts[tcp_opt_cnt]);
+                            ptrdiff_t diff = tcp_opts[tcp_opt_cnt].data - (uint8_t *)p->tcph;
+                            DEBUG_VALIDATE_BUG_ON(diff > UINT16_MAX);
+                            p->tcpvars.sack_set = true;
+                            p->tcpvars.sack_cnt = (olen - 2) / 8;
+                            p->tcpvars.sack_offset = (uint16_t)diff;
                         }
                     }
                     break;
@@ -518,7 +522,6 @@ end:
 
 static int TCPGetSackTest01(void)
 {
-    int retval = 0;
     static uint8_t raw_tcp[] = {
         0x00, 0x50, 0x06, 0xa6, 0xfa, 0x87, 0x0b, 0xf5,
         0xf1, 0x59, 0x02, 0xe0, 0xa0, 0x10, 0x3e, 0xbc,
@@ -529,12 +532,11 @@ static int TCPGetSackTest01(void)
         0xf1, 0x59, 0x13, 0xfc, 0xf1, 0x59, 0x1f, 0x64,
         0xf1, 0x59, 0x08, 0x94, 0xf1, 0x59, 0x0e, 0x48 };
     Packet *p = PacketGetFromAlloc();
-    if (unlikely(p == NULL))
+    FAIL_IF_NULL(p);
-        return 0;
+
     IPV4Hdr ip4h;
     ThreadVars tv;
     DecodeThreadVars dtv;
-
     memset(&tv, 0, sizeof(ThreadVars));
     memset(&dtv, 0, sizeof(DecodeThreadVars));
     memset(&ip4h, 0, sizeof(IPV4Hdr));
@@ -546,39 +548,22 @@ static int TCPGetSackTest01(void)
     FlowInitConfig(FLOW_QUIET);
     DecodeTCP(&tv, &dtv, p, raw_tcp, sizeof(raw_tcp));
 
-    if (p->tcph == NULL) {
+    FAIL_IF_NULL(p->tcph);
-        printf("tcp packet decode failed: ");
-        goto end;
-    }
 
-    if (!TCP_HAS_SACK(p)) {
+    FAIL_IF(!TCP_HAS_SACK(p));
-        printf("tcp packet sack not decoded: ");
-        goto end;
-    }
 
     int sack = TCP_GET_SACK_CNT(p);
-    if (sack != 2) {
+    FAIL_IF(sack != 2);
-        printf("expected 2 sack records, got %u: ", TCP_GET_SACK_CNT(p));
-        goto end;
-    }
 
     const uint8_t *sackptr = TCP_GET_SACK_PTR(p);
-    if (sackptr == NULL) {
+    FAIL_IF_NULL(sackptr);
-        printf("no sack data: ");
-        goto end;
-    }
 
-    if (memcmp(sackptr, raw_tcp_sack, 16) != 0) {
+    FAIL_IF(memcmp(sackptr, raw_tcp_sack, 16) != 0);
-        printf("malformed sack data: ");
-        goto end;
-    }
 
-    retval = 1;
-end:
     PacketRecycle(p);
     FlowShutdown();
     SCFree(p);
-    return retval;
+    PASS;
 }
 #endif /* UNITTESTS */
 

src/decode-tcp.h

@@ -91,7 +91,7 @@
 #define TCP_GET_TSECR(p)                    ((p)->tcpvars.ts_ecr)
 
 #define TCP_HAS_WSCALE(p)                   ((p)->tcpvars.wscale_set)
-#define TCP_HAS_SACK(p)                     ((p)->tcpvars.sack.type == TCP_OPT_SACK)
+#define TCP_HAS_SACK(p)                     (p)->tcpvars.sack_set
 #define TCP_HAS_TS(p)                       ((p)->tcpvars.ts_set)
 #define TCP_HAS_MSS(p)                      ((p)->tcpvars.mss_set)
 #define TCP_HAS_TFO(p)                      ((p)->tcpvars.tfo_set)
@@ -100,8 +100,8 @@
 #define TCP_GET_WSCALE(p) (p)->tcpvars.wscale
 
 #define TCP_GET_SACKOK(p)                    (p)->tcpvars.sack_ok
-#define TCP_GET_SACK_PTR(p)                  TCP_HAS_SACK((p)) ? (p)->tcpvars.sack.data : NULL
+#define TCP_GET_SACK_PTR(p)                  ((uint8_t *)(p)->tcph) + (p)->tcpvars.sack_offset
-#define TCP_GET_SACK_CNT(p)                  (TCP_HAS_SACK((p)) ? (((p)->tcpvars.sack.len - 2) / 8) : 0)
+#define TCP_GET_SACK_CNT(p)                  (p)->tcpvars.sack_cnt
 #define TCP_GET_MSS(p)                       (p)->tcpvars.mss
 
 #define TCP_GET_OFFSET(p)                    TCP_GET_RAW_OFFSET((p)->tcph)
@@ -164,7 +164,9 @@ typedef struct TCPVars_
     uint16_t stream_pkt_flags;
     uint32_t ts_val;    /* host-order */
     uint32_t ts_ecr;    /* host-order */
-    TCPOpt sack;
+    bool sack_set;
+    uint8_t sack_cnt;     /**< number of sack records */
+    uint16_t sack_offset; /**< offset relative to tcp header start */
 } TCPVars;
 
 #define CLEAR_TCP_PACKET(p)                                                                        \