diff --git a/third_party/tcplp/bsdtcp/cc.h b/third_party/tcplp/bsdtcp/cc.h
index 408c5ced4..a213f5546 100644
--- a/third_party/tcplp/bsdtcp/cc.h
+++ b/third_party/tcplp/bsdtcp/cc.h
@@ -57,8 +57,8 @@
  * the global linked list are removed.
  */
 
-#ifndef _NETINET_CC_H_
-#define _NETINET_CC_H_
+#ifndef TCPLP_NETINET_CC_H_
+#define TCPLP_NETINET_CC_H_
 
 /* XXX: TCP_CA_NAME_MAX define lives in tcp.h for compat reasons. */
 #include "tcp.h"
diff --git a/third_party/tcplp/bsdtcp/cc/cc_module.h b/third_party/tcplp/bsdtcp/cc/cc_module.h
index a38a1f353..9d83f296f 100644
--- a/third_party/tcplp/bsdtcp/cc/cc_module.h
+++ b/third_party/tcplp/bsdtcp/cc/cc_module.h
@@ -40,8 +40,8 @@
  *   http://caia.swin.edu.au/urp/newtcp/
  */
 
-#ifndef _NETINET_CC_MODULE_H_
-#define _NETINET_CC_MODULE_H_
+#ifndef TCPLP_NETINET_CC_MODULE_H_
+#define TCPLP_NETINET_CC_MODULE_H_
 
 /* samkumar: This was already commented out in FreeBSD (I didn't do it). */
 /*
diff --git a/third_party/tcplp/bsdtcp/icmp_var.h b/third_party/tcplp/bsdtcp/icmp_var.h
index 4f0cc2d29..2767b8244 100644
--- a/third_party/tcplp/bsdtcp/icmp_var.h
+++ b/third_party/tcplp/bsdtcp/icmp_var.h
@@ -35,8 +35,8 @@
  * weren't necessary (and often introduced additional dependencies).
  */
 
-#ifndef _NETINET_ICMP_VAR_H_
-#define _NETINET_ICMP_VAR_H_
+#ifndef TCPLP_NETINET_ICMP_VAR_H_
+#define TCPLP_NETINET_ICMP_VAR_H_
 /*
  * Identifiers for ICMP sysctl nodes
  */
diff --git a/third_party/tcplp/bsdtcp/ip.h b/third_party/tcplp/bsdtcp/ip.h
index 7f70196fe..247c6f816 100644
--- a/third_party/tcplp/bsdtcp/ip.h
+++ b/third_party/tcplp/bsdtcp/ip.h
@@ -31,8 +31,8 @@
  * $FreeBSD$
  */
 
-#ifndef _NETINET_IP_H_
-#define	_NETINET_IP_H_
+#ifndef TCPLP_NETINET_IP_H_
+#define TCPLP_NETINET_IP_H_
 
 #define	IP_MAXPACKET	65535		/* maximum packet size */
 
diff --git a/third_party/tcplp/bsdtcp/ip6.h b/third_party/tcplp/bsdtcp/ip6.h
index cc079240f..3326d266f 100644
--- a/third_party/tcplp/bsdtcp/ip6.h
+++ b/third_party/tcplp/bsdtcp/ip6.h
@@ -61,8 +61,8 @@
  *	@(#)ip.h	8.1 (Berkeley) 6/10/93
  */
 
-#ifndef _NETINET_IP6_H_
-#define _NETINET_IP6_H_
+#ifndef TCPLP_NETINET_IP6_H_
+#define TCPLP_NETINET_IP6_H_
 
 #include "types.h"
 
diff --git a/third_party/tcplp/bsdtcp/sys/queue.h b/third_party/tcplp/bsdtcp/sys/queue.h
index bbd1c46a9..4ed5c7c8f 100644
--- a/third_party/tcplp/bsdtcp/sys/queue.h
+++ b/third_party/tcplp/bsdtcp/sys/queue.h
@@ -30,8 +30,8 @@
  * $FreeBSD$
  */
 
-#ifndef _SYS_QUEUE_H_
-#define	_SYS_QUEUE_H_
+#ifndef TCPLP_SYS_QUEUE_H_
+#define	TCPLP_SYS_QUEUE_H_
 
 /* samkumar: Removing this, as it adds yet another dependency. */
 //#include <sys/cdefs.h>
diff --git a/third_party/tcplp/bsdtcp/tcp.h b/third_party/tcplp/bsdtcp/tcp.h
index c51217a7e..63c66d02f 100644
--- a/third_party/tcplp/bsdtcp/tcp.h
+++ b/third_party/tcplp/bsdtcp/tcp.h
@@ -37,8 +37,8 @@
  * we should look at that very closely, and consider rewriting it.
  */
 
-#ifndef _NETINET_TCP_H_
-#define _NETINET_TCP_H_
+#ifndef TCPLP_NETINET_TCP_H_
+#define TCPLP_NETINET_TCP_H_
 
 #include <stdint.h>
 #include <stdio.h>
@@ -61,14 +61,28 @@ struct tcphdr {
 	uint16_t	th_dport;		/* destination port */
 	tcp_seq	th_seq;			/* sequence number */
 	tcp_seq	th_ack;			/* acknowledgement number */
-#if 1 //BYTE_ORDER == LITTLE_ENDIAN
+
+	/*
+	 * samkumar: The original FreeBSD code used bit fields for the offset and
+	 * unused bits, within this byte. I've rewritten it to avoid the use of
+	 * bit fields, so that the code is more portable. The original code, which
+	 * defined the order of bit fields based on the platform's endianness, is
+	 * included below, commented out using "#if 0".
+	 */
+	uint8_t th_off_x2; /* data offset and unused bits */
+#define	TH_OFF_SHIFT	4
+
+#if 0
+#if BYTE_ORDER == LITTLE_ENDIAN
 	uint8_t	th_x2:4,		/* (unused) */
 		th_off:4;		/* data offset */
 #endif
-#if 0 //BYTE_ORDER == BIG_ENDIAN
+#if BYTE_ORDER == BIG_ENDIAN
 	uint8_t	th_off:4,		/* data offset */
 		th_x2:4;		/* (unused) */
 #endif
+#endif
+
 	uint8_t	th_flags;
 #define	TH_FIN	0x01
 #define	TH_SYN	0x02
diff --git a/third_party/tcplp/bsdtcp/tcp_const.h b/third_party/tcplp/bsdtcp/tcp_const.h
index 31af20944..6728fa6ed 100644
--- a/third_party/tcplp/bsdtcp/tcp_const.h
+++ b/third_party/tcplp/bsdtcp/tcp_const.h
@@ -35,8 +35,8 @@
  * often serve to enable, disable, or configure certain TCP-related features.
  */
 
-#ifndef _TCP_CONST_H_
-#define _TCP_CONST_H_
+#ifndef TCPLP_TCP_CONST_H_
+#define TCPLP_TCP_CONST_H_
 
 #include "../tcplp.h"
 
diff --git a/third_party/tcplp/bsdtcp/tcp_fsm.h b/third_party/tcplp/bsdtcp/tcp_fsm.h
index 110e9e3cc..4edc35127 100644
--- a/third_party/tcplp/bsdtcp/tcp_fsm.h
+++ b/third_party/tcplp/bsdtcp/tcp_fsm.h
@@ -33,8 +33,8 @@
 
 /* samkumar: Removed some #ifdef guards around constants needed for TCPlp. */
 
-#ifndef _NETINET_TCP_FSM_H_
-#define	_NETINET_TCP_FSM_H_
+#ifndef TCPLP_NETINET_TCP_FSM_H_
+#define	TCPLP_NETINET_TCP_FSM_H_
 
 #include "types.h"
 
diff --git a/third_party/tcplp/bsdtcp/tcp_input.c b/third_party/tcplp/bsdtcp/tcp_input.c
index b00a31a93..5c4773085 100644
--- a/third_party/tcplp/bsdtcp/tcp_input.c
+++ b/third_party/tcplp/bsdtcp/tcp_input.c
@@ -476,7 +476,7 @@ tcp_input(struct ip6_hdr* ip6, struct tcphdr* th, otMessage* msg, struct tcpcb*
 
 	/*
 	 * samkumar: Logic that handled IPv4 was deleted below. I won't add a
-	 * comment everytime this is done, but I'm putting it here (one of the
+	 * comment every time this is done, but I'm putting it here (one of the
 	 * first instances of this) for clarity.
 	 */
 	iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
@@ -485,7 +485,7 @@ tcp_input(struct ip6_hdr* ip6, struct tcphdr* th, otMessage* msg, struct tcpcb*
 	 * Check that TCP offset makes sense,
 	 * pull out TCP options and adjust length.		XXX
 	 */
-	off = th->th_off << 2;
+	off = (th->th_off_x2 >> TH_OFF_SHIFT) << 2;
 	if (off < sizeof (struct tcphdr) || off > tlen) {
 		goto drop;
 	}
@@ -1030,7 +1030,7 @@ tcp_do_segment(struct ip6_hdr* ip6, struct tcphdr *th, otMessage* msg,
 	 * Parse options on any incoming segment.
 	 */
 	tcp_dooptions(&to, (uint8_t *)(th + 1),
-	    (th->th_off << 2) - sizeof(struct tcphdr),
+	    ((th->th_off_x2 >> TH_OFF_SHIFT) << 2) - sizeof(struct tcphdr),
 	    (thflags & TH_SYN) ? TO_SYN : 0);
 
 	/*
diff --git a/third_party/tcplp/bsdtcp/tcp_output.c b/third_party/tcplp/bsdtcp/tcp_output.c
index 695257b79..5f6139b06 100644
--- a/third_party/tcplp/bsdtcp/tcp_output.c
+++ b/third_party/tcplp/bsdtcp/tcp_output.c
@@ -1037,7 +1037,7 @@ send:
 	th->th_ack = htonl(tp->rcv_nxt);
 	if (optlen) {
 		bcopy(opt, th + 1, optlen);
-		th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
+		th->th_off_x2 = ((sizeof (struct tcphdr) + optlen) >> 2) << TH_OFF_SHIFT;
 	}
 	th->th_flags = flags;
 	/*
diff --git a/third_party/tcplp/bsdtcp/tcp_seq.h b/third_party/tcplp/bsdtcp/tcp_seq.h
index 09cbb1d29..c3caae453 100644
--- a/third_party/tcplp/bsdtcp/tcp_seq.h
+++ b/third_party/tcplp/bsdtcp/tcp_seq.h
@@ -30,8 +30,8 @@
  * $FreeBSD$
  */
 
-#ifndef _NETINET_TCP_SEQ_H_
-#define _NETINET_TCP_SEQ_H_
+#ifndef TCPLP_NETINET_TCP_SEQ_H_
+#define TCPLP_NETINET_TCP_SEQ_H_
 
 #include "../tcplp.h"
 
diff --git a/third_party/tcplp/bsdtcp/tcp_subr.c b/third_party/tcplp/bsdtcp/tcp_subr.c
index 0774b478b..d90461c97 100644
--- a/third_party/tcplp/bsdtcp/tcp_subr.c
+++ b/third_party/tcplp/bsdtcp/tcp_subr.c
@@ -41,6 +41,7 @@
 #include "tcp_var.h"
 #include "tcp_seq.h"
 #include "tcp_timer.h"
+#include "sys/queue.h"
 #include "../lib/bitmap.h"
 #include "../lib/cbuf.h"
 #include "cc.h"
@@ -234,15 +235,16 @@ tcpip_fillheaders(struct tcpcb* tp, otMessageInfo* ip_ptr, void *tcp_ptr)
 	memcpy(&ip_ptr->mPeerAddr, &tp->faddr, sizeof(ip_ptr->mPeerAddr));
 
 	/* Fill in the TCP header */
-	/* samkumar: I kept the old code for ports commented out, for reference. */
+	/* samkumar: I kept the old code commented out, for reference. */
 	//th->th_sport = inp->inp_lport;
 	//th->th_dport = inp->inp_fport;
 	th->th_sport = tp->lport;
 	th->th_dport = tp->fport;
 	th->th_seq = 0;
 	th->th_ack = 0;
-	th->th_x2 = 0;
-	th->th_off = 5;
+	// th->th_x2 = 0;
+	// th->th_off = 5;
+	th->th_off_x2 = (5 << TH_OFF_SHIFT);
 	th->th_flags = 0;
 	th->th_win = 0;
 	th->th_urp = 0;
@@ -309,8 +311,10 @@ tcp_respond(struct tcpcb *tp, otInstance* instance, struct ip6_hdr* ip6gen, stru
 	nth->th_dport = thgen->th_sport;
 	nth->th_seq = htonl(seq);
 	nth->th_ack = htonl(ack);
-	nth->th_x2 = 0;
-	nth->th_off = sizeof(struct tcphdr) >> 2;
+	/* samkumar: original code for setting th_x2 and th_off, for reference. */
+	// nth->th_x2 = 0;
+	// nth->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
+	nth->th_off_x2 = (sizeof(struct tcphdr) >> 2) << TH_OFF_SHIFT;
 	nth->th_flags = flags;
 	if (tp != NULL)
 		nth->th_win = htons((uint16_t) (win >> tp->rcv_scale));
diff --git a/third_party/tcplp/bsdtcp/tcp_timer.h b/third_party/tcplp/bsdtcp/tcp_timer.h
index 331ac242e..03389f84a 100644
--- a/third_party/tcplp/bsdtcp/tcp_timer.h
+++ b/third_party/tcplp/bsdtcp/tcp_timer.h
@@ -38,8 +38,8 @@
  * parameters) and global statistics (e.g. tcp_keepcnt).
  */
 
-#ifndef _NETINET_TCP_TIMER_H_
-#define _NETINET_TCP_TIMER_H_
+#ifndef TCPLP_NETINET_TCP_TIMER_H_
+#define TCPLP_NETINET_TCP_TIMER_H_
 
 #include "tcp_var.h"
 
diff --git a/third_party/tcplp/bsdtcp/tcp_timewait.c b/third_party/tcplp/bsdtcp/tcp_timewait.c
index 07e2c9ecc..61ef74836 100644
--- a/third_party/tcplp/bsdtcp/tcp_timewait.c
+++ b/third_party/tcplp/bsdtcp/tcp_timewait.c
@@ -158,8 +158,7 @@ tcp_twrespond(struct tcpcb* tp, int flags)
 	nth->th_dport = tp->fport;
 	nth->th_seq = htonl(tp->snd_nxt);
 	nth->th_ack = htonl(tp->rcv_nxt);
-	nth->th_x2 = 0;
-	nth->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
+	nth->th_off_x2 = ((sizeof(struct tcphdr) + optlen) >> 2) << TH_OFF_SHIFT;
 	nth->th_flags = flags;
 	nth->th_win = htons(tp->tw_last_win);
 	nth->th_urp = 0;
diff --git a/third_party/tcplp/bsdtcp/tcp_var.h b/third_party/tcplp/bsdtcp/tcp_var.h
index 489b80213..56890ff92 100644
--- a/third_party/tcplp/bsdtcp/tcp_var.h
+++ b/third_party/tcplp/bsdtcp/tcp_var.h
@@ -30,8 +30,8 @@
  * $FreeBSD$
  */
 
-#ifndef _NETINET_TCP_VAR_H_
-#define _NETINET_TCP_VAR_H_
+#ifndef TCPLP_NETINET_TCP_VAR_H_
+#define TCPLP_NETINET_TCP_VAR_H_
 
 /* For memmove(). */
 #include <string.h>
@@ -50,8 +50,6 @@
 #include "types.h"
 #include "ip6.h"
 
-#include "sys/queue.h"
-
 /* Implement byte-order-specific functions using OpenThread. */
 uint16_t tcplp_sys_hostswap16(uint16_t hostport);
 uint32_t tcplp_sys_hostswap32(uint32_t hostport);
@@ -104,7 +102,19 @@ struct sackhole {
 	tcp_seq start;		/* start seq no. of hole */
 	tcp_seq end;		/* end seq no. */
 	tcp_seq rxmit;		/* next seq. no in hole to be retransmitted */
-	TAILQ_ENTRY(sackhole) scblink;	/* scoreboard linkage */
+
+	/*
+	 * samkumar: I'm using this instead of the TAILQ_ENTRY macro to avoid
+	 * including sys/queue.h from this file. It's undesirable to include
+	 * sys/queue.h from this file because this file is part of the external
+	 * interface to TCPlp, and sys/queue.h pollutes the global namespace.
+	 * The original code that uses TAILQ_ENTRY is in a comment below.
+	 */
+	struct {
+		struct sackhole *tqe_next;	/* next element */
+		struct sackhole **tqe_prev;	/* address of previous next element */
+	} scblink;	/* scoreboard linkage */
+	// TAILQ_ENTRY(sackhole) scblink;	/* scoreboard linkage */
 };
 
 struct sackhint {
@@ -200,7 +210,7 @@ struct tcpcb {
 	int	t_segqlen;		/* segment reassembly queue length */
 #endif
 
-	int	t_dupacks;		/* consecutive dup acks recd */
+	int32_t	t_dupacks;		/* consecutive dup acks recd */
 
 #if 0
 	struct tcp_timer *t_timers;	/* All the TCP timers in one struct */
@@ -228,8 +238,8 @@ struct tcpcb {
 
 	tcp_seq	rcv_nxt;		/* receive next */
 	tcp_seq	rcv_adv;		/* advertised window */
-	uint64_t	rcv_wnd;		/* receive window */
 	tcp_seq	rcv_up;			/* receive urgent pointer */
+	uint64_t	rcv_wnd;		/* receive window */
 
 	uint64_t	snd_wnd;		/* send window */
 	uint64_t	snd_cwnd;		/* congestion-controlled window */
@@ -251,22 +261,37 @@ struct tcpcb {
 //	uint32_t	t_bw_spare1;		/* unused */
 //	tcp_seq	t_bw_spare2;		/* unused */
 
-	int	t_rxtcur;		/* current retransmit value (ticks) */
+	int32_t	t_rxtcur;		/* current retransmit value (ticks) */
 	uint32_t	t_maxseg;		/* maximum segment size */
-	int	t_srtt;			/* smoothed round-trip time */
-	int	t_rttvar;		/* variance in round-trip time */
+	int32_t	t_srtt;			/* smoothed round-trip time */
+	int32_t	t_rttvar;		/* variance in round-trip time */
 
-	int	t_rxtshift;		/* log(2) of rexmt exp. backoff */
+	int32_t	t_rxtshift;		/* log(2) of rexmt exp. backoff */
 	uint32_t	t_rttmin;		/* minimum rtt allowed */
 	uint32_t	t_rttbest;		/* best rtt we've seen */
+
+	int32_t	t_softerror;		/* possible error not yet reported */
+
 	uint64_t	t_rttupdated;		/* number of times rtt sampled */
 	uint64_t	max_sndwnd;		/* largest window peer has offered */
-
-	int	t_softerror;		/* possible error not yet reported */
 /* out-of-band data */
 //	char	t_oobflags;		/* have some */
 //	char	t_iobc;			/* input character */
+
+	tcp_seq	last_ack_sent;
+/* experimental */
+	tcp_seq	snd_recover_prev;	/* snd_recover prior to retransmit */
+	uint64_t	snd_cwnd_prev;		/* cwnd prior to retransmit */
+	uint64_t	snd_ssthresh_prev;	/* ssthresh prior to retransmit */
+//	int	t_sndzerowin;		/* zero-window updates sent */
+	uint32_t	t_badrxtwin;		/* window for retransmit recovery */
+	uint8_t	snd_limited;		/* segments limited transmitted */
+
 /* RFC 1323 variables */
+/*
+ * samkumar: Moved "RFC 1323 variables" after "experimental" to reduce
+ * compiler-inserted padding.
+ */
 	uint8_t	snd_scale;		/* window scaling for send window */
 	uint8_t	rcv_scale;		/* window scaling for recv window */
 	uint8_t	request_r_scale;	/* pending window scaling */
@@ -274,27 +299,28 @@ struct tcpcb {
 	uint32_t	ts_recent_age;		/* when last updated */
 	u_int32_t  ts_offset;		/* our timestamp offset */
 
-	tcp_seq	last_ack_sent;
-/* experimental */
-	uint64_t	snd_cwnd_prev;		/* cwnd prior to retransmit */
-	uint64_t	snd_ssthresh_prev;	/* ssthresh prior to retransmit */
-	tcp_seq	snd_recover_prev;	/* snd_recover prior to retransmit */
-//	int	t_sndzerowin;		/* zero-window updates sent */
-	uint32_t	t_badrxtwin;		/* window for retransmit recovery */
-	uint8_t	snd_limited;		/* segments limited transmitted */
-
 /* SACK related state */
-	int	snd_numholes;		/* number of holes seen by sender */
-	TAILQ_HEAD(sackhole_head, sackhole) snd_holes;
+	int32_t	snd_numholes;		/* number of holes seen by sender */
+	/*
+	 * samkumar: I replaced the TAILQ_HEAD macro invocation (commented out
+	 * below) with the code it stands for, to avoid having to #include
+	 * sys/queue.h in this file. See the comment above in struct sackhole for
+	 * more info.
+	 */
+	struct sackhole_head {
+		struct sackhole *tqh_first;	/* first element */
+		struct sackhole **tqh_last;	/* addr of last next element */
+	} snd_holes;
+	// TAILQ_HEAD(sackhole_head, sackhole) snd_holes;
 					/* SACK scoreboard (sorted) */
 	tcp_seq	snd_fack;		/* last seq number(+1) sack'd by rcv'r*/
-	int	rcv_numsacks;		/* # distinct sack blks present */
+	int32_t	rcv_numsacks;		/* # distinct sack blks present */
 	struct sackblk sackblks[MAX_SACK_BLKS]; /* seq nos. of sack blocks */
 	tcp_seq sack_newdata;		/* New data xmitted in this recovery
 					   episode starts at this seq number */
 	struct sackhint	sackhint;	/* SACK scoreboard hint */
 
-	int	t_rttlow;		/* smallest observed RTT */
+	int32_t	t_rttlow;		/* smallest observed RTT */
 #if 0
 	u_int32_t	rfbuf_ts;	/* recv buffer autoscaling timestamp */
 	int	rfbuf_cnt;		/* recv buffer autoscaling byte count */
@@ -303,7 +329,7 @@ struct tcpcb {
 //	int	t_sndrexmitpack;	/* retransmit packets sent */
 //	int	t_rcvoopack;		/* out-of-order packets received */
 //	void	*t_toe;			/* TOE pcb pointer */
-	int	t_bytes_acked;		/* # bytes acked during current RTT */
+	int32_t	t_bytes_acked;		/* # bytes acked during current RTT */
 //	struct cc_algo	*cc_algo;	/* congestion control algorithm */
 	struct cc_var	ccv[1];		/* congestion control specific vars */
 #if 0
diff --git a/third_party/tcplp/bsdtcp/types.h b/third_party/tcplp/bsdtcp/types.h
index 650eb15ce..cf1176cf5 100644
--- a/third_party/tcplp/bsdtcp/types.h
+++ b/third_party/tcplp/bsdtcp/types.h
@@ -46,8 +46,8 @@
  * standard integer types (uint8_t, uint16_t, etc.).
  */
 
-#ifndef _SYS_TYPES_H_
-#define	_SYS_TYPES_H_
+#ifndef TCPLP_SYS_TYPES_H_
+#define TCPLP_SYS_TYPES_H_
 
 #include <stdint.h>