From: Guy Harris <guy@alum.mit.edu>
Date: Sun, 16 Feb 2014 04:37:28 +0000 (-0800)
Subject: Add {40,48,56}-bit big-endian extract macros and use them for DCCP ACKs.
X-Git-Tag: tcpdump-4.6.0~225
X-Git-Url: https://git.tcpdump.org/tcpdump/commitdiff_plain/f5e2e1a4a523dde5afbcd73ec3999c0093605d36

Add {40,48,56}-bit big-endian extract macros and use them for DCCP ACKs.

Add macros to, given an octet pointer, extract 40-bit, 48-bit, and
56-bit big-endian numbers from the location pointed to by that pointer,
and use them when extracting ACK numbers from DCCP packets.  This fixes
problems on big-endian(!) machines.
---

diff --git a/extract.h b/extract.h
index 4dfbaae3..fe69bbcc 100644
--- a/extract.h
+++ b/extract.h
@@ -165,6 +165,30 @@ EXTRACT_64BITS(const void *p)
 		     (u_int32_t)*((const u_int8_t *)(p) + 1) << 8 | \
 		     (u_int32_t)*((const u_int8_t *)(p) + 2)))
 
+#define EXTRACT_40BITS(p) \
+	((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 32 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 1) << 24 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 2) << 16 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 3) << 8 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 4)))
+
+#define EXTRACT_48BITS(p) \
+	((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 40 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 1) << 32 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 2) << 24 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 3) << 16 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 4) << 8 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 5)))
+
+#define EXTRACT_56BITS(p) \
+	((u_int64_t)((u_int64_t)*((const u_int8_t *)(p) + 0) << 48 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 1) << 40 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 2) << 32 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 3) << 24 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 4) << 16 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 5) << 8 | \
+		     (u_int64_t)*((const u_int8_t *)(p) + 6)))
+
 /*
  * Macros to extract possibly-unaligned little-endian integral values.
  * XXX - do loads on little-endian machines that support unaligned loads?
diff --git a/print-dccp.c b/print-dccp.c
index 06ea2cd1..fcc2cc1c 100644
--- a/print-dccp.c
+++ b/print-dccp.c
@@ -226,23 +226,15 @@ static inline unsigned int dccp_basic_hdr_len(const struct dccp_hdr *dh)
 static void dccp_print_ack_no(const u_char *bp)
 {
 	const struct dccp_hdr *dh = (const struct dccp_hdr *)bp;
-	const struct dccp_hdr_ack_bits *dh_ack =
-		(struct dccp_hdr_ack_bits *)(bp + dccp_basic_hdr_len(dh));
-	u_int32_t ack_high;
+	const u_char *ackp = bp + dccp_basic_hdr_len(dh);
 	u_int64_t ackno;
 
-	TCHECK2(*dh_ack,4);
-	ack_high = DCCPH_ACK(dh_ack);
-	ackno = EXTRACT_24BITS(&ack_high) & 0xFFFFFF;
-
 	if (DCCPH_X(dh) != 0) {
-		u_int32_t ack_low;
-
-		TCHECK2(*dh_ack,8);
-		ack_low = dh_ack->dccph_ack_nr_low;
-
-		ackno &= 0x00FFFF;  /* clear reserved field */
-		ackno = (ackno << 32) + EXTRACT_32BITS(&ack_low);
+		TCHECK2(*ackp, 8);
+		ackno = EXTRACT_48BITS(ackp + 2);
+	} else {
+		TCHECK2(*ackp, 4);
+		ackno = EXTRACT_24BITS(ackp + 1);
 	}
 
 	(void)printf("(ack=%" PRIu64 ") ", ackno);