Replace some seeks forward with wtap_read_bytes() with a null buffer pointer.

If the seek forward is just skipping record content that's not
(currently) interesting, use wtap_read_bytes() with a null buffer
pointer; it catches short "reads" and requires less seeking, so it may
work better when reading from a pipe.

Change-Id: Ifb07d20e0391a8ed97da85149d971b4e9ef093a8
Reviewed-on: https://code.wireshark.org/review/17976
Reviewed-by: Guy Harris <guy@alum.mit.edu>

11 files changed, 42 insertions, 28 deletions

diff --git a/wiretap/5views.c b/wiretap/5views.c
index 1c693a4c58..3ee32d17e9 100644
--- a/wiretap/5views.c
+++ b/wiretap/5views.c
@@ -211,7 +211,7 @@ _5views_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
 		/*
 		 * Not a packet - skip to the next record.
 		 */
-		if (file_seek(wth->fh, TimeStamped_Header.RecSize, SEEK_CUR, err) == -1)
+		if (!wtap_read_bytes(wth->fh, NULL, TimeStamped_Header.RecSize, err, err_info))
 			return FALSE;
 	} while (1);
 
diff --git a/wiretap/lanalyzer.c b/wiretap/lanalyzer.c
index 6e6f3f49dc..e18604246e 100644
--- a/wiretap/lanalyzer.c
+++ b/wiretap/lanalyzer.c
@@ -424,7 +424,8 @@ wtap_open_return_val lanalyzer_open(wtap *wth, int *err, gchar **err_info)
                   return WTAP_OPEN_MINE;
 
             default:
-                  if (file_seek(wth->fh, record_length, SEEK_CUR, err) == -1) {
+                  /* Unknown record type - skip it */
+                  if (!wtap_read_bytes(wth->fh, NULL, record_length, err, err_info)) {
                         return WTAP_OPEN_ERROR;
                   }
                   break;
diff --git a/wiretap/libpcap.c b/wiretap/libpcap.c
index e8903b9e3c..e0133e2dc9 100644
--- a/wiretap/libpcap.c
+++ b/wiretap/libpcap.c
@@ -494,7 +494,7 @@ static int libpcap_try(wtap *wth, int *err, gchar **err_info)
 	 * Now skip over the first record's data, under the assumption
 	 * that the header is sane.
 	 */
-	if (file_seek(wth->fh, first_rec_hdr.hdr.incl_len, SEEK_CUR, err) == -1)
+	if (!wtap_read_bytes(wth->fh, NULL, first_rec_hdr.hdr.incl_len, err, err_info))
 		return -1;
 
 	/*
diff --git a/wiretap/mp2t.c b/wiretap/mp2t.c
index 44ee0b728c..5507eef3bd 100644
--- a/wiretap/mp2t.c
+++ b/wiretap/mp2t.c
@@ -120,7 +120,7 @@ mp2t_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
 
     /* if there's a trailer, skip it and go to the start of the next packet */
     if (mp2t->trailer_len!=0) {
-        if (-1 == file_seek(wth->fh, mp2t->trailer_len, SEEK_CUR, err)) {
+        if (!wtap_read_bytes(wth->fh, NULL, mp2t->trailer_len, err, err_info)) {
             return FALSE;
         }
     }
diff --git a/wiretap/nettl.c b/wiretap/nettl.c
index c8481fe899..22cb007c6e 100644
--- a/wiretap/nettl.c
+++ b/wiretap/nettl.c
@@ -354,7 +354,8 @@ nettl_read_rec(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr, Buffer *buf,
         return FALSE;
     subsys = g_ntohs(rec_hdr.subsys);
     hdr_len -= NETTL_REC_HDR_LEN;
-    if (file_seek(fh, hdr_len, SEEK_CUR, err) == -1)
+    /* Skip the rest of the header. */
+    if (!wtap_read_bytes(fh, NULL, hdr_len, err, err_info))
         return FALSE;
 
     if ( (pntoh32(&rec_hdr.kind) & NETTL_HDR_PDU_MASK) == 0 ) {
@@ -443,7 +444,7 @@ nettl_read_rec(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr, Buffer *buf,
                         return FALSE;
                     /* padding is usually either a total 11 or 16 bytes??? */
                     padlen = (int)dummyc[8];
-                    if (file_seek(fh, padlen, SEEK_CUR, err) == -1)
+                    if (!wtap_read_bytes(fh, NULL, padlen, err, err_info))
                         return FALSE;
                     padlen += 9;
                 }
@@ -451,12 +452,12 @@ nettl_read_rec(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr, Buffer *buf,
                      || (subsys == NETTL_SUBSYS_EISA_FDDI)
                      || (subsys == NETTL_SUBSYS_HSC_FDDI) ) {
                 /* other flavor FDDI cards have an extra 3 bytes of padding */
-                if (file_seek(fh, 3, SEEK_CUR, err) == -1)
+                if (!wtap_read_bytes(fh, NULL, 3, err, err_info))
                     return FALSE;
                 padlen = 3;
             } else if (subsys == NETTL_SUBSYS_NS_LS_LOOPBACK) {
                 /* LOOPBACK has an extra 26 bytes of padding */
-                if (file_seek(fh, 26, SEEK_CUR, err) == -1)
+                if (!wtap_read_bytes(fh, NULL, 26, err, err_info))
                     return FALSE;
                 padlen = 26;
             } else if (subsys == NETTL_SUBSYS_NS_LS_SCTP) {
@@ -470,7 +471,7 @@ nettl_read_rec(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr, Buffer *buf,
                  *   1 = Inbound
                  *   2 = Outbound
                  */
-                if (file_seek(fh, 8, SEEK_CUR, err) == -1)
+                if (!wtap_read_bytes(fh, NULL, 8, err, err_info))
                     return FALSE;
                 padlen = 8;
             } else {
@@ -497,7 +498,8 @@ nettl_read_rec(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr, Buffer *buf,
              * And what are the extra two bytes?
              */
             if (nettl->is_hpux_11) {
-                if (file_seek(fh, 2, SEEK_CUR, err) == -1) return FALSE;
+                if (!wtap_read_bytes(fh, NULL, 2, err, err_info))
+                    return FALSE;
             }
             padlen = 0;
             break;
@@ -526,7 +528,7 @@ nettl_read_rec(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr, Buffer *buf,
             length = pntoh32(&rec_hdr.length);
             caplen = pntoh32(&rec_hdr.caplen);
             padlen = 24;        /* sizeof (struct nettlrec_sx25l2_hdr) - NETTL_REC_HDR_LEN + 4 */
-            if (file_seek(fh, padlen, SEEK_CUR, err) == -1)
+            if (!wtap_read_bytes(fh, NULL, padlen, err, err_info))
                 return FALSE;
             break;
 
diff --git a/wiretap/network_instruments.c b/wiretap/network_instruments.c
index 286243a312..19ff6fbba8 100644
--- a/wiretap/network_instruments.c
+++ b/wiretap/network_instruments.c
@@ -170,6 +170,7 @@ wtap_open_return_val network_instruments_open(wtap *wth, int *err, gchar **err_i
         /* process (or skip over) the current TLV */
         switch (tlvh.type) {
         case INFORMATION_TYPE_TIME_INFO:
+            /* XXX - what if tlvh.length != sizeof sizeof private_state->time_format? */
             if (!wtap_read_bytes(wth->fh, &private_state->time_format,
                                  sizeof private_state->time_format,
                                  err, err_info))
@@ -180,7 +181,7 @@ wtap_open_return_val network_instruments_open(wtap *wth, int *err, gchar **err_i
         default:
             seek_increment = tlvh.length - (int)sizeof tlvh;
             if (seek_increment > 0) {
-                if (file_seek(wth->fh, seek_increment, SEEK_CUR, err) == -1)
+                if (!wtap_read_bytes(wth->fh, NULL, seek_increment, err, err_info))
                     return WTAP_OPEN_ERROR;
             }
             offset += seek_increment;
@@ -196,7 +197,7 @@ wtap_open_return_val network_instruments_open(wtap *wth, int *err, gchar **err_i
     }
     seek_increment = header_offset - offset;
     if (seek_increment > 0) {
-        if (file_seek(wth->fh, seek_increment, SEEK_CUR, err) == -1)
+        if (!wtap_read_bytes(wth->fh, NULL, seek_increment, err, err_info))
             return WTAP_OPEN_ERROR;
     }
 
@@ -401,6 +402,7 @@ read_packet_header(wtap *wth, FILE_T fh, union wtap_pseudo_header *pseudo_header
         /* process (or skip over) the current TLV */
         switch (tlvh.type) {
         case INFORMATION_TYPE_WIRELESS:
+            /* XXX - what if tlvh.length != sizeof wireless_header? */
             if (!wtap_read_bytes(fh, &wireless_header, sizeof wireless_header,
                                  err, err_info))
                 return -1;
@@ -419,7 +421,7 @@ read_packet_header(wtap *wth, FILE_T fh, union wtap_pseudo_header *pseudo_header
             /* skip the TLV data */
             seek_increment = tlvh.length - (int)sizeof tlvh;
             if (seek_increment > 0) {
-                if (file_seek(fh, seek_increment, SEEK_CUR, err) == -1)
+                if (!wtap_read_bytes(fh, NULL, seek_increment, err, err_info))
                     return -1;
             }
             offset += seek_increment;
@@ -524,7 +526,7 @@ read_packet_data(FILE_T fh, int offset_to_frame, int current_offset_from_packet_
     /* skip to the packet data */
     seek_increment = offset_to_frame - current_offset_from_packet_header;
     if (seek_increment > 0) {
-        if (file_seek(fh, seek_increment, SEEK_CUR, err) == -1) {
+        if (!wtap_read_bytes(fh, NULL, seek_increment, err, err_info)) {
             return -1;
         }
         bytes_consumed += seek_increment;
@@ -558,7 +560,7 @@ skip_to_next_packet(wtap *wth, int offset_to_next_packet, int current_offset_fro
     /* skip to the next packet header */
     seek_increment = offset_to_next_packet - current_offset_from_packet_header;
     if (seek_increment > 0) {
-        if (file_seek(wth->fh, seek_increment, SEEK_CUR, err) == -1)
+        if (!wtap_read_bytes(wth->fh, NULL, seek_increment, err, err_info))
             return FALSE;
     }
 
diff --git a/wiretap/netxray.c b/wiretap/netxray.c
index 8d09a0e335..cf1d6fb41c 100644
--- a/wiretap/netxray.c
+++ b/wiretap/netxray.c
@@ -1061,7 +1061,7 @@ reread:
 	/*
 	 * If there's extra stuff at the end of the record, skip it.
 	 */
-	if (file_seek(wth->fh, padding, SEEK_CUR, err) == -1)
+	if (!wtap_read_bytes(wth->fh, NULL, padding, err, err_info))
 		return FALSE;
 
 	/*
diff --git a/wiretap/peektagged.c b/wiretap/peektagged.c
index 6d46e26fa9..943ca0e058 100644
--- a/wiretap/peektagged.c
+++ b/wiretap/peektagged.c
@@ -372,8 +372,9 @@ wtap_open_return_val peektagged_open(wtap *wth, int *err, gchar **err_info)
     }
 
     /* skip 8 zero bytes */
-    if (file_seek (wth->fh, 8L, SEEK_CUR, err) == -1)
-        return WTAP_OPEN_NOT_MINE;
+    if (!wtap_read_bytes (wth->fh, NULL, 8, err, err_info)) {
+        return WTAP_OPEN_ERROR;
+    }
 
     /*
      * This is an Peek tagged file.
diff --git a/wiretap/radcom.c b/wiretap/radcom.c
index e7fc81946b..f86b1f3e23 100644
--- a/wiretap/radcom.c
+++ b/wiretap/radcom.c
@@ -144,8 +144,13 @@ wtap_open_return_val radcom_open(wtap *wth, int *err, gchar **err_info)
 		return WTAP_OPEN_NOT_MINE;
 	}
 
-	if (file_seek(wth->fh, sizeof(struct frame_date), SEEK_CUR, err) == -1)
-		return WTAP_OPEN_ERROR;
+	/* So what time is this? */
+	if (!wtap_read_bytes(wth->fh, NULL, sizeof(struct frame_date),
+	    err, err_info)) {
+		if (*err != WTAP_ERR_SHORT_READ)
+			return WTAP_OPEN_ERROR;
+		return WTAP_OPEN_NOT_MINE;
+	}
 
 	for (;;) {
 		if (!wtap_read_bytes(wth->fh, search_encap, 4,
@@ -167,8 +172,11 @@ wtap_open_return_val radcom_open(wtap *wth, int *err, gchar **err_info)
 		if (file_seek(wth->fh, -3, SEEK_CUR, err) == -1)
 			return WTAP_OPEN_ERROR;
 	}
-	if (file_seek(wth->fh, 12, SEEK_CUR, err) == -1)
-		return WTAP_OPEN_ERROR;
+	if (!wtap_read_bytes(wth->fh, NULL, 12, err, err_info)) {
+		if (*err != WTAP_ERR_SHORT_READ)
+			return WTAP_OPEN_ERROR;
+		return WTAP_OPEN_NOT_MINE;
+	}
 	if (!wtap_read_bytes(wth->fh, search_encap, 4, err, err_info)) {
 		if (*err != WTAP_ERR_SHORT_READ)
 			return WTAP_OPEN_ERROR;
@@ -220,13 +228,13 @@ wtap_open_return_val radcom_open(wtap *wth, int *err, gchar **err_info)
 #endif
 
 	if (wth->file_encap == WTAP_ENCAP_ETHERNET) {
-		if (file_seek(wth->fh, 294, SEEK_CUR, err) == -1)
+		if (!wtap_read_bytes(wth->fh, NULL, 294, err, err_info))
 			return WTAP_OPEN_ERROR;
 	} else if (wth->file_encap == WTAP_ENCAP_LAPB) {
-		if (file_seek(wth->fh, 297, SEEK_CUR, err) == -1)
+		if (!wtap_read_bytes(wth->fh, NULL, 297, err, err_info))
 			return WTAP_OPEN_ERROR;
 	} else if (wth->file_encap == WTAP_ENCAP_ATM_RFC1483) {
-		if (file_seek(wth->fh, 504, SEEK_CUR, err) == -1)
+		if (!wtap_read_bytes(wth->fh, NULL, 504, err, err_info))
 			return WTAP_OPEN_ERROR;
 	}
 
diff --git a/wiretap/snoop.c b/wiretap/snoop.c
index 6939c6c752..1831e422c6 100644
--- a/wiretap/snoop.c
+++ b/wiretap/snoop.c
@@ -735,7 +735,7 @@ snoop_read_shomiti_wireless_pseudoheader(FILE_T fh,
 	}
 	/* Skip the header. */
 	rsize = ((int) whdr.pad[3]) - 8;
-	if (file_seek(fh, rsize, SEEK_CUR, err) == -1)
+	if (!wtap_read_bytes(fh, NULL, rsize, err, err_info))
 		return FALSE;
 
 	memset(&pseudo_header->ieee_802_11, 0, sizeof(pseudo_header->ieee_802_11));
diff --git a/wiretap/vwr.c b/wiretap/vwr.c
index 9088c60a54..b125759f2f 100644
--- a/wiretap/vwr.c
+++ b/wiretap/vwr.c
@@ -779,7 +779,7 @@ static int vwr_get_fpga_version(wtap *wth, int *err, gchar **err_info)
                 return UNKNOWN_FPGA;
             }
             else if (v_type != VT_FRAME) {
-                if (file_seek(wth->fh, f_len, SEEK_CUR, err) < 0) {
+                if (!wtap_read_bytes(wth->fh, NULL, f_len, err, err_info)) {
                     g_free(rec);
                     return -1;
                 }