Index: sys/kern/uipc_debug.c
===================================================================
--- sys/kern/uipc_debug.c
+++ sys/kern/uipc_debug.c
@@ -75,7 +75,7 @@
 }
 
 static void
-db_print_sooptions(short so_options)
+db_print_sooptions(int so_options)
 {
 	int comma;
 
@@ -120,6 +120,10 @@
 		db_printf("%sSO_REUSEPORT", comma ? ", " : "");
 		comma = 1;
 	}
+	if (so_options & SO_REUSEPORT_LB) {
+		db_printf("%sSO_REUSEPORT_LB", comma ? ", " : "");
+		comma = 1;
+	}
 	if (so_options & SO_TIMESTAMP) {
 		db_printf("%sSO_TIMESTAMP", comma ? ", " : "");
 		comma = 1;
Index: sys/kern/uipc_socket.c
===================================================================
--- sys/kern/uipc_socket.c
+++ sys/kern/uipc_socket.c
@@ -1055,6 +1055,102 @@
 	sodealloc(so);
 }
 
+/*
+ * Let socket in same load balance group (same port and address)
+ * inherit pending sockets of the closing socket.
+ *
+ * "so_inh" will inherit sockets from "so"
+ */
+void
+soinherit(struct socket *so, struct socket *so_inh)
+{
+	TAILQ_HEAD(, socket) comp, incomp;
+	struct socket *sp, *head, *head_inh;
+	int qlen, incqlen;
+
+	KASSERT(so->so_options & SO_ACCEPTCONN,
+	    ("so does not accept connection"));
+	KASSERT(so_inh->so_options & SO_ACCEPTCONN,
+	    ("so_inh does not accept connection"));
+
+
+restart:
+	SOCK_LOCK(so);
+	if ((head = so->so_listen) != NULL &&
+	    __predict_false(SOLISTEN_TRYLOCK(head) == 0)) {
+		SOCK_UNLOCK(so);
+		goto restart;
+	}
+
+restart_inh:
+	SOCK_LOCK(so_inh);
+	if ((head_inh = so_inh->so_listen) != NULL &&
+	    __predict_false(SOLISTEN_TRYLOCK(head_inh) == 0)) {
+		SOCK_UNLOCK(so_inh);
+		goto restart_inh;
+	}
+
+	TAILQ_INIT(&comp);
+	TAILQ_INIT(&incomp);
+
+	/*
+	 * Save completed queue and incompleted queue
+	 */
+	TAILQ_CONCAT(&comp, &so->sol_comp, so_list);
+	qlen = so->sol_qlen;
+	so->sol_qlen = 0;
+
+	TAILQ_CONCAT(&incomp, &so->sol_incomp, so_list);
+	incqlen = so->sol_incqlen;
+	so->sol_incqlen = 0;
+
+	/*
+	 * Append the saved completed queue and incompleted
+	 * queue to the socket inherits them.
+	 *
+	 * XXX
+	 * This may temporarily break the inheriting socket's
+	 * so_qlimit.
+	 */
+	TAILQ_FOREACH(sp, &comp, so_list) {
+		refcount_acquire(&so_inh->so_count);
+		sp->so_listen = so_inh;
+		sp->inherit = 1;
+		crfree(sp->so_cred);
+		sp->so_cred = crhold(so_inh->so_cred);
+	}
+
+	TAILQ_FOREACH(sp, &incomp, so_list) {
+		refcount_acquire(&so_inh->so_count);
+		sp->inherit = 1;
+		sp->so_listen = so_inh;
+		crfree(sp->so_cred);
+		sp->so_cred = crhold(so_inh->so_cred);
+	}
+
+	TAILQ_CONCAT(&so_inh->sol_comp, &comp, so_list);
+	so_inh->sol_qlen += qlen;
+
+	TAILQ_CONCAT(&so_inh->sol_incomp, &incomp, so_list);
+	so_inh->sol_incqlen += incqlen;
+
+	SOCK_UNLOCK(so);
+	if(head != NULL)
+		SOLISTEN_UNLOCK(head);
+
+	SOCK_UNLOCK(so_inh);
+	if(head_inh != NULL) {
+		if(qlen > 0) {
+			/*
+			 * "New" connections have arrived
+			 */
+			solisten_wakeup(head_inh);
+		} else {
+			SOLISTEN_UNLOCK(head_inh);
+		}
+	}
+}
+
 /*
  * Close a socket on last file table reference removal.  Initiate disconnect
  * if connected.  Free socket when disconnect complete.
@@ -2775,6 +2870,7 @@
 		case SO_BROADCAST:
 		case SO_REUSEADDR:
 		case SO_REUSEPORT:
+		case SO_REUSEPORT_LB:
 		case SO_OOBINLINE:
 		case SO_TIMESTAMP:
 		case SO_BINTIME:
@@ -2993,6 +3089,7 @@
 		case SO_KEEPALIVE:
 		case SO_REUSEADDR:
 		case SO_REUSEPORT:
+		case SO_REUSEPORT_LB:
 		case SO_BROADCAST:
 		case SO_OOBINLINE:
 		case SO_ACCEPTCONN:
Index: sys/netinet/in_pcb.h
===================================================================
--- sys/netinet/in_pcb.h
+++ sys/netinet/in_pcb.h
@@ -76,6 +76,11 @@
 	struct	in_addr	ia46_addr4;
 };
 
+union in_dependaddr {
+	struct in_addr_4in6 id46_addr;
+	struct in6_addr	id6_addr;
+};
+
 /*
  * NOTE: ipv6 addrs should be 64-bit aligned, per RFC 2553.  in_conninfo has
  * some extra padding to accomplish this.
@@ -86,22 +91,14 @@
 	u_int16_t	ie_fport;		/* foreign port */
 	u_int16_t	ie_lport;		/* local port */
 	/* protocol dependent part, local and foreign addr */
-	union {
-		/* foreign host table entry */
-		struct	in_addr_4in6 ie46_foreign;
-		struct	in6_addr ie6_foreign;
-	} ie_dependfaddr;
-	union {
-		/* local host table entry */
-		struct	in_addr_4in6 ie46_local;
-		struct	in6_addr ie6_local;
-	} ie_dependladdr;
+	union in_dependaddr ie_dependfaddr;	/* foreign host table entry */
+	union in_dependaddr ie_dependladdr;	/* local host table entry */
+#define	ie_faddr	ie_dependfaddr.id46_addr.ia46_addr4
+#define	ie_laddr	ie_dependladdr.id46_addr.ia46_addr4
+#define	ie6_faddr	ie_dependfaddr.id6_addr
+#define	ie6_laddr	ie_dependladdr.id6_addr
 	u_int32_t	ie6_zoneid;		/* scope zone id */
 };
-#define	ie_faddr	ie_dependfaddr.ie46_foreign.ia46_addr4
-#define	ie_laddr	ie_dependladdr.ie46_local.ia46_addr4
-#define	ie6_faddr	ie_dependfaddr.ie6_foreign
-#define	ie6_laddr	ie_dependladdr.ie6_local
 
 /*
  * XXX The defines for inc_* are hacks and should be changed to direct
@@ -328,6 +325,21 @@
 	u_short phd_port;
 };
 
+struct inpcblbgroup {
+	LIST_ENTRY(inpcblbgroup) il_list;
+	uint16_t	il_lport;
+	u_char		il_vflag;
+	u_char		il_pad;
+	uint32_t	il_pad2;
+	union in_dependaddr il_dependladdr;
+#define il_laddr	il_dependladdr.id46_addr.ia46_addr4
+#define il6_laddr	il_dependladdr.id6_addr
+	uint32_t	il_inpsiz; /* size of il_inp[] */
+	uint32_t	il_inpcnt; /* # of elem in il_inp[] */
+	struct inpcb	*il_inp[];
+};
+LIST_HEAD(inpcblbgrouphead, inpcblbgroup);
+
 /*-
  * Global data structure for each high-level protocol (UDP, TCP, ...) in both
  * IPv4 and IPv6.  Holds inpcb lists and information for managing them.
@@ -420,6 +432,13 @@
 	struct inpcbhead	*ipi_wildbase;		/* (p) */
 	u_long			 ipi_wildmask;		/* (p) */
 
+	/*
+	 * Load balanced group used by the SO_REUSEPORT_LB option,
+	 * hashed by local address and local port.
+	 */
+	struct	inpcblbgrouphead *ipi_lbgrouphashbase;
+	u_long	ipi_lbgrouphashmask;
+
 	/*
 	 * Pointer to network stack instance
 	 */
@@ -506,7 +525,7 @@
 	inp_inpcbtotcpcb(struct inpcb *inp);
 void 	inp_4tuple_get(struct inpcb *inp, uint32_t *laddr, uint16_t *lp,
 		uint32_t *faddr, uint16_t *fp);
-short	inp_so_options(const struct inpcb *inp);
+int		inp_so_options(const struct inpcb *inp);
 
 #endif /* _KERNEL */
 
@@ -569,6 +588,10 @@
 	(((faddr) ^ ((faddr) >> 16) ^ ntohs((lport) ^ (fport))) & (mask))
 #define INP_PCBPORTHASH(lport, mask) \
 	(ntohs((lport)) & (mask))
+#define INP_PCBLBGROUP_PORTHASH(lport, mask) \
+	(ntohs((lport)) & (mask))
+#define INP_PCBLBGROUP_PKTHASH(faddr, lport, fport) \
+	((faddr) ^ ((faddr) >> 16) ^ ntohs((lport) ^ (fport)))
 #define	INP6_PCBHASHKEY(faddr)	((faddr)->s6_addr32[3])
 
 /*
@@ -624,7 +647,7 @@
 /*
  * Flags for inp_flags2.
  */
-#define	INP_LLE_VALID		0x00000001 /* cached lle is valid */	
+#define	INP_LLE_VALID		0x00000001 /* cached lle is valid */ 
 #define	INP_RT_VALID		0x00000002 /* cached rtentry is valid */
 #define	INP_PCBGROUPWILD	0x00000004 /* in pcbgroup wildcard list */
 #define	INP_REUSEPORT		0x00000008 /* SO_REUSEPORT option is set */
@@ -636,6 +659,7 @@
 #define	INP_RECVRSSBUCKETID	0x00000200 /* populate recv datagram with bucket id */
 #define	INP_RATE_LIMIT_CHANGED	0x00000400 /* rate limit needs attention */
 #define	INP_ORIGDSTADDR		0x00000800 /* receive IP dst address/port */
+#define	INP_REUSEPORT_LB	0x00001000 /* SO_REUSEPORT_LB option is set */
 
 /*
  * Flags passed to in_pcblookup*() functions.
@@ -738,6 +762,8 @@
 struct inpcb *
 	in_pcblookup(struct inpcbinfo *, struct in_addr, u_int,
 	    struct in_addr, u_int, int, struct ifnet *);
+struct inpcb *
+	in_pcblookup_lbgroup_last(const struct inpcb *inp);
 struct inpcb *
 	in_pcblookup_mbuf(struct inpcbinfo *, struct in_addr, u_int,
 	    struct in_addr, u_int, int, struct ifnet *, struct mbuf *);
Index: sys/netinet/in_pcb.c
===================================================================
--- sys/netinet/in_pcb.c
+++ sys/netinet/in_pcb.c
@@ -102,6 +102,9 @@
 
 #include <security/mac/mac_framework.h>
 
+#define INPCBLBGROUP_SIZMIN	8
+#define INPCBLBGROUP_SIZMAX	256
+
 static struct callout	ipport_tick_callout;
 
 /*
@@ -211,6 +214,173 @@
  * functions often modify hash chains or addresses in pcbs.
  */
 
+static struct inpcblbgroup *
+in_pcblbgroup_alloc(struct inpcblbgrouphead *hdr, u_char vflag,
+    uint16_t port, const union in_dependaddr *addr, int size)
+{
+	struct inpcblbgroup *grp;
+
+	size_t bytes = __offsetof(struct inpcblbgroup, il_inp[size]);
+	grp = malloc(bytes, M_PCB, M_WAITOK | M_ZERO);
+	grp->il_vflag = vflag;
+	grp->il_lport = port;
+	grp->il_dependladdr = *addr;
+	grp->il_inpsiz = size;
+	LIST_INSERT_HEAD(hdr, grp, il_list);
+
+	return grp;
+}
+
+static void
+in_pcblbgroup_free(struct inpcblbgroup *grp)
+{
+	LIST_REMOVE(grp, il_list);
+	free(grp, M_TEMP);
+}
+
+static struct inpcblbgroup *
+in_pcblbgroup_resize(struct inpcblbgrouphead *hdr,
+    struct inpcblbgroup *old_grp, int size)
+{
+	struct inpcblbgroup *grp;
+	int i;
+
+	grp = in_pcblbgroup_alloc(hdr, old_grp->il_vflag,
+	    old_grp->il_lport, &old_grp->il_dependladdr, size);
+
+	KASSERT(old_grp->il_inpcnt < grp->il_inpsiz,
+	    ("invalid new local group size %d and old local group count %d",
+	     grp->il_inpsiz, old_grp->il_inpcnt));
+	for (i = 0; i < old_grp->il_inpcnt; ++i)
+		grp->il_inp[i] = old_grp->il_inp[i];
+	grp->il_inpcnt = old_grp->il_inpcnt;
+
+	in_pcblbgroup_free(old_grp);
+
+	return grp;
+}
+
+/*
+ * Add PCB to lb group (load balance used by SO_REUSEPORT_LB)
+ */
+static void
+in_pcbinslbgrouphash(struct inpcb *inp, struct inpcbinfo *pcbinfo)
+{
+	struct inpcblbgrouphead *hdr;
+	struct inpcblbgroup *grp;
+
+	uint16_t hashmask = pcbinfo->ipi_lbgrouphashmask;
+	uint16_t lport = inp->inp_lport;
+	uint32_t group_index = INP_PCBLBGROUP_PORTHASH(lport, hashmask);
+
+	hdr = &pcbinfo->ipi_lbgrouphashbase[group_index];
+
+	struct ucred *cred;
+
+	if (pcbinfo->ipi_lbgrouphashbase == NULL)
+		return;
+
+	/*
+	 * don't allow jailed socket to join local group
+	 */
+	if (inp->inp_socket != NULL)
+		cred = inp->inp_socket->so_cred;
+	else
+		cred = NULL;
+	if (cred != NULL && jailed(cred))
+		return;
+
+#ifdef INET6
+	/*
+	 * don't allow IPv4 mapped INET6 wild socket
+	 */
+	if ((inp->inp_vflag & INP_IPV4) &&
+	    inp->inp_laddr.s_addr == INADDR_ANY &&
+	    INP_CHECK_SOCKAF(inp->inp_socket, AF_INET6))
+		return;
+#endif
+
+	hdr = &pcbinfo->ipi_lbgrouphashbase[
+	    INP_PCBLBGROUP_PORTHASH(inp->inp_lport, pcbinfo->ipi_lbgrouphashmask)];
+
+	LIST_FOREACH(grp, hdr, il_list) {
+		if (grp->il_vflag == inp->inp_vflag &&
+		    grp->il_lport == inp->inp_lport &&
+		    memcmp(&grp->il_dependladdr,
+		        &inp->inp_inc.inc_ie.ie_dependladdr,
+		        sizeof(grp->il_dependladdr)) == 0) {
+			break;
+		}
+	}
+	if (grp == NULL) {
+		/* Create new local group */
+		grp = in_pcblbgroup_alloc(hdr, inp->inp_vflag,
+		    inp->inp_lport, &inp->inp_inc.inc_ie.ie_dependladdr,
+		    INPCBLBGROUP_SIZMIN);
+	} else if (grp->il_inpcnt == grp->il_inpsiz) {
+		if (grp->il_inpsiz >= INPCBLBGROUP_SIZMAX) {
+			static int limit_logged = 0;
+
+			if (!limit_logged) {
+				limit_logged = 1;
+				printf("lb group port %d, "
+					   "limit reached\n", ntohs(grp->il_lport));
+			}
+			return;
+		}
+
+		/* Expand this local group */
+		grp = in_pcblbgroup_resize(hdr, grp, grp->il_inpsiz * 2);
+	}
+
+	KASSERT(grp->il_inpcnt < grp->il_inpsiz,
+			("invalid local group size %d and count %d",
+			 grp->il_inpsiz, grp->il_inpcnt));
+
+	grp->il_inp[grp->il_inpcnt] = inp;
+	grp->il_inpcnt++;
+}
+
+static void
+in_pcbremlbgrouphash(struct inpcb *inp, struct inpcbinfo *pcbinfo)
+{
+	struct inpcblbgrouphead *hdr;
+	struct inpcblbgroup *grp;
+
+	if (pcbinfo->ipi_lbgrouphashbase == NULL)
+		return;
+
+	hdr = &pcbinfo->ipi_lbgrouphashbase[
+	    INP_PCBLBGROUP_PORTHASH(inp->inp_lport, pcbinfo->ipi_lbgrouphashmask)];
+
+	LIST_FOREACH(grp, hdr, il_list) {
+		int i;
+
+		for (i = 0; i < grp->il_inpcnt; ++i) {
+			if (grp->il_inp[i] != inp)
+				continue;
+
+			if (grp->il_inpcnt == 1) {
+				/* Free this local group */
+				in_pcblbgroup_free(grp);
+			} else {
+				/* Pull up inpcbs */
+				for (; i + 1 < grp->il_inpcnt; ++i)
+					grp->il_inp[i] = grp->il_inp[i + 1];
+				grp->il_inpcnt--;
+
+				if (grp->il_inpsiz > INPCBLBGROUP_SIZMIN &&
+				    grp->il_inpcnt <= (grp->il_inpsiz / 4)) {
+					/* Shrink this local group */
+					grp = in_pcblbgroup_resize(hdr, grp,
+							   grp->il_inpsiz / 2);
+				}
+			}
+			return;
+		}
+	}
+}
+
 /*
  * Different protocols initialize their inpcbs differently - giving
  * different name to the lock.  But they all are disposed the same.
@@ -246,6 +416,8 @@
 	    &pcbinfo->ipi_hashmask);
 	pcbinfo->ipi_porthashbase = hashinit(porthash_nelements, M_PCB,
 	    &pcbinfo->ipi_porthashmask);
+	pcbinfo->ipi_lbgrouphashbase = hashinit(hash_nelements, M_PCB,
+	    &pcbinfo->ipi_lbgrouphashmask);
 #ifdef PCBGROUP
 	in_pcbgroup_init(pcbinfo, hashfields, hash_nelements);
 #endif
@@ -269,6 +441,8 @@
 	hashdestroy(pcbinfo->ipi_hashbase, M_PCB, pcbinfo->ipi_hashmask);
 	hashdestroy(pcbinfo->ipi_porthashbase, M_PCB,
 	    pcbinfo->ipi_porthashmask);
+	hashdestroy(pcbinfo->ipi_lbgrouphashbase, M_PCB,
+	    pcbinfo->ipi_lbgrouphashmask);
 #ifdef PCBGROUP
 	in_pcbgroup_destroy(pcbinfo);
 #endif
@@ -507,18 +681,20 @@
 /*
  * Return cached socket options.
  */
-short
+int
 inp_so_options(const struct inpcb *inp)
 {
-   short so_options;
+	int so_options;
 
-   so_options = 0;
+	so_options = 0;
 
-   if ((inp->inp_flags2 & INP_REUSEPORT) != 0)
-	   so_options |= SO_REUSEPORT;
-   if ((inp->inp_flags2 & INP_REUSEADDR) != 0)
-	   so_options |= SO_REUSEADDR;
-   return (so_options);
+	if ((inp->inp_flags2 & INP_REUSEPORT_LB) != 0)
+		so_options |= SO_REUSEPORT_LB;
+	if ((inp->inp_flags2 & INP_REUSEPORT) != 0)
+		so_options |= SO_REUSEPORT;
+	if ((inp->inp_flags2 & INP_REUSEADDR) != 0)
+		so_options |= SO_REUSEADDR;
+	return (so_options);
 }
 #endif /* INET || INET6 */
 
@@ -574,6 +750,12 @@
 	int lookupflags = 0, reuseport = (so->so_options & SO_REUSEPORT);
 	int error;
 
+	/*
+	 * XXX Maybe we could let SO_REUSEPORT_LB set SO_REUSEPORT bit here
+	 * so that we don't have to add to the (already messy) code below
+	 */
+	int reuseport_lb = (so->so_options & SO_REUSEPORT_LB);
+
 	/*
 	 * No state changes, so read locks are sufficient here.
 	 */
@@ -585,7 +767,7 @@
 	laddr.s_addr = *laddrp;
 	if (nam != NULL && laddr.s_addr != INADDR_ANY)
 		return (EINVAL);
-	if ((so->so_options & (SO_REUSEADDR|SO_REUSEPORT)) == 0)
+	if ((so->so_options & (SO_REUSEADDR|SO_REUSEPORT|SO_REUSEPORT_LB)) == 0)
 		lookupflags = INPLOOKUP_WILDCARD;
 	if (nam == NULL) {
 		if ((error = prison_local_ip4(cred, &laddr)) != 0)
@@ -620,18 +802,23 @@
 			 * and a multicast address is bound on both
 			 * new and duplicated sockets.
 			 */
+
+			// XXX: How to deal with SO_REUSEPORT_LB here?
+			// Added equivalent treatment as SO_REUSEPORT here for now
+			if ((so->so_options & (SO_REUSEADDR|SO_REUSEPORT_LB)) != 0)
+				reuseport_lb = SO_REUSEADDR|SO_REUSEPORT_LB;
 			if ((so->so_options & (SO_REUSEADDR|SO_REUSEPORT)) != 0)
 				reuseport = SO_REUSEADDR|SO_REUSEPORT;
 		} else if (sin->sin_addr.s_addr != INADDR_ANY) {
 			sin->sin_port = 0;		/* yech... */
 			bzero(&sin->sin_zero, sizeof(sin->sin_zero));
 			/*
-			 * Is the address a local IP address? 
+			 * Is the address a local IP address?
 			 * If INP_BINDANY is set, then the socket may be bound
 			 * to any endpoint address, local or not.
 			 */
 			if ((inp->inp_flags & INP_BINDANY) == 0 &&
-			    ifa_ifwithaddr_check((struct sockaddr *)sin) == 0) 
+			    ifa_ifwithaddr_check((struct sockaddr *)sin) == 0)
 				return (EADDRNOTAVAIL);
 		}
 		laddr = sin->sin_addr;
@@ -661,7 +848,8 @@
 				     ntohl(t->inp_faddr.s_addr) == INADDR_ANY) &&
 				    (ntohl(sin->sin_addr.s_addr) != INADDR_ANY ||
 				     ntohl(t->inp_laddr.s_addr) != INADDR_ANY ||
-				     (t->inp_flags2 & INP_REUSEPORT) == 0) &&
+				     (t->inp_flags2 & INP_REUSEPORT) ||
+				     (t->inp_flags2 & INP_REUSEPORT_LB) == 0) &&
 				    (inp->inp_cred->cr_uid !=
 				     t->inp_cred->cr_uid))
 					return (EADDRINUSE);
@@ -686,11 +874,14 @@
 				 */
 				tw = intotw(t);
 				if (tw == NULL ||
-				    (reuseport & tw->tw_so_options) == 0)
+				    ((reuseport & tw->tw_so_options) == 0 &&
+					(reuseport_lb & tw->tw_so_options) == 0)) {
 					return (EADDRINUSE);
+				}
 			} else if (t &&
-			    ((inp->inp_flags2 & INP_BINDMULTI) == 0) &&
-			    (reuseport & inp_so_options(t)) == 0) {
+				   ((inp->inp_flags2 & INP_BINDMULTI) == 0) &&
+				   (reuseport & inp_so_options(t)) == 0 &&
+				   (reuseport_lb & inp_so_options(t)) == 0) {
 #ifdef INET6
 				if (ntohl(sin->sin_addr.s_addr) !=
 				    INADDR_ANY ||
@@ -699,7 +890,7 @@
 				    (inp->inp_vflag & INP_IPV6PROTO) == 0 ||
 				    (t->inp_vflag & INP_IPV6PROTO) == 0)
 #endif
-				return (EADDRINUSE);
+						return (EADDRINUSE);
 				if (t && (! in_pcbbind_check_bindmulti(inp, t)))
 					return (EADDRINUSE);
 			}
@@ -1360,6 +1551,7 @@
 		struct inpcbport *phd = inp->inp_phd;
 
 		INP_HASH_WLOCK(inp->inp_pcbinfo);
+		in_pcbremlbgrouphash(inp, inp->inp_pcbinfo);
 		LIST_REMOVE(inp, inp_hash);
 		LIST_REMOVE(inp, inp_portlist);
 		if (LIST_FIRST(&phd->phd_pcblist) == NULL) {
@@ -1620,6 +1812,100 @@
 }
 #undef INP_LOOKUP_MAPPED_PCB_COST
 
+struct inpcb *
+in_pcblookup_lbgroup_last(const struct inpcb *inp)
+{
+	const struct inpcbinfo *pcbinfo = inp->inp_pcbinfo;
+	const struct inpcblbgrouphead *hdr;
+	const struct inpcblbgroup *grp;
+	int i;
+
+	if (pcbinfo->ipi_lbgrouphashbase == NULL)
+		return NULL;
+
+	hdr = &pcbinfo->ipi_lbgrouphashbase[
+	    INP_PCBLBGROUP_PORTHASH(inp->inp_lport, pcbinfo->ipi_lbgrouphashmask)];
+
+	LIST_FOREACH(grp, hdr, il_list) {
+		if (grp->il_vflag == inp->inp_vflag &&
+		    grp->il_lport == inp->inp_lport &&
+		    memcmp(&grp->il_dependladdr,
+			&inp->inp_inc.inc_ie.ie_dependladdr,
+			sizeof(grp->il_dependladdr)) == 0) {
+			break;
+		}
+	}
+	if (grp == NULL || grp->il_inpcnt == 1)
+		return NULL;
+
+	KASSERT(grp->il_inpcnt >= 2,
+	    ("invalid lbgroup inp count %d", grp->il_inpcnt));
+	for (i = 0; i < grp->il_inpcnt; ++i) {
+		if (grp->il_inp[i] == inp) {
+			int last = grp->il_inpcnt - 1;
+
+			if (i == last)
+				last = grp->il_inpcnt - 2;
+			printf("%s] returning inp at index %d (last)\n", __func__, last);
+			return grp->il_inp[last];
+		}
+	}
+	printf("%s] returning NULL\n", __func__);
+	return NULL;
+}
+
+static struct inpcb *
+in_pcblookup_lbgroup(const struct inpcbinfo *pcbinfo,
+  const struct in_addr *laddr, uint16_t lport, const struct in_addr *faddr,
+  uint16_t fport, int lookupflags)
+{
+	struct inpcb *local_wild = NULL;
+	const struct inpcblbgrouphead *hdr;
+	struct inpcblbgroup *grp;
+	struct inpcblbgroup *grp_local_wild;
+
+	hdr = &pcbinfo->ipi_lbgrouphashbase[
+		  INP_PCBLBGROUP_PORTHASH(lport, pcbinfo->ipi_lbgrouphashmask)];
+
+	/*
+	 * Order of socket selection:
+	 * 1. non-wild.
+	 * 2. wild (if lookupflags contains INPLOOKUP_WILDCARD).
+	 *
+	 * NOTE:
+	 * - Local group does not contain jailed sockets
+	 * - Local group does not contain IPv4 mapped INET6 wild sockets
+	 */
+	LIST_FOREACH(grp, hdr, il_list) {
+#ifdef INET6
+		if (!(grp->il_vflag & INP_IPV4))
+			continue;
+#endif
+
+		if (grp->il_lport == lport) {
+
+			uint32_t idx = 0;
+			int pkt_hash = INP_PCBLBGROUP_PKTHASH(faddr->s_addr, lport, fport);
+
+			idx = pkt_hash % grp->il_inpcnt;
+
+			if (grp->il_laddr.s_addr == laddr->s_addr) {
+				return grp->il_inp[idx];
+			} else {
+				if (grp->il_laddr.s_addr == INADDR_ANY &&
+					(lookupflags & INPLOOKUP_WILDCARD)) {
+					local_wild = grp->il_inp[idx];
+					grp_local_wild = grp;
+				}
+			}
+		}
+	}
+	if (local_wild != NULL) {
+		return local_wild;
+	}
+	return NULL;
+}
+
 #ifdef PCBGROUP
 /*
  * Lookup PCB in hash list, using pcbgroup tables.
@@ -1883,6 +2169,16 @@
 	if (tmpinp != NULL)
 		return (tmpinp);
 
+	/*
+	 * Then look in lb group
+	 */
+	if (pcbinfo->ipi_lbgrouphashbase != NULL) {
+		inp = in_pcblookup_lbgroup(pcbinfo, &laddr, lport, &faddr, fport, lookupflags);
+		if (inp != NULL) {
+			return inp;
+		}
+	}
+
 	/*
 	 * Then look for a wildcard match, if requested.
 	 */
@@ -2085,6 +2381,7 @@
 	struct inpcbinfo *pcbinfo = inp->inp_pcbinfo;
 	struct inpcbport *phd;
 	u_int32_t hashkey_faddr;
+	int so_options;
 
 	INP_WLOCK_ASSERT(inp);
 	INP_HASH_WLOCK_ASSERT(pcbinfo);
@@ -2105,6 +2402,16 @@
 	pcbporthash = &pcbinfo->ipi_porthashbase[
 	    INP_PCBPORTHASH(inp->inp_lport, pcbinfo->ipi_porthashmask)];
 
+
+	/*
+	 * Add entry in lb group
+	 * Only do this if SO_REUSEPORT_LB is set
+	 */
+	so_options = inp_so_options(inp);
+	if(so_options & SO_REUSEPORT_LB) {
+		in_pcbinslbgrouphash(inp, pcbinfo);
+	}
+
 	/*
 	 * Go through port list and look for a head for this lport.
 	 */
@@ -2231,6 +2538,10 @@
 		struct inpcbport *phd = inp->inp_phd;
 
 		INP_HASH_WLOCK(pcbinfo);
+
+		// XXX Only do if SO_REUSEPORT_LB set?
+		in_pcbremlbgrouphash(inp, pcbinfo);
+
 		LIST_REMOVE(inp, inp_hash);
 		LIST_REMOVE(inp, inp_portlist);
 		if (LIST_FIRST(&phd->phd_pcblist) == NULL) {
Index: sys/netinet/ip_output.c
===================================================================
--- sys/netinet/ip_output.c
+++ sys/netinet/ip_output.c
@@ -987,6 +987,15 @@
 				INP_WUNLOCK(inp);
 				error = 0;
 				break;
+			case SO_REUSEPORT_LB:
+				INP_WLOCK(inp);
+				if ((so->so_options & SO_REUSEPORT_LB) != 0)
+					inp->inp_flags2 |= INP_REUSEPORT_LB;
+				else
+					inp->inp_flags2 &= ~INP_REUSEPORT_LB;
+				INP_WUNLOCK(inp);
+				error = 0;
+				break;
 			case SO_SETFIB:
 				INP_WLOCK(inp);
 				inp->inp_inc.inc_fibnum = so->so_fibnum;
Index: sys/netinet/tcp_subr.c
===================================================================
--- sys/netinet/tcp_subr.c
+++ sys/netinet/tcp_subr.c
@@ -1633,10 +1633,28 @@
 {
 	struct inpcb *inp = tp->t_inpcb;
 	struct socket *so;
+	struct inpcb *inp_inh = NULL;
+	int listen = tp->t_state & TCPS_LISTEN;
 
 	INP_INFO_LOCK_ASSERT(&V_tcbinfo);
 	INP_WLOCK_ASSERT(inp);
 
+	if (listen) {
+		/*
+		 * Pending socket/syncache inheritance
+		 *
+		 * If this is a listen(2) socket, find another listen(2)
+		 * socket in the same local group, which could inherit
+		 * the syncache and sockets pending on the completion
+		 * and incompletion queues.
+		 *
+		 * NOTE:
+		 * Currently the inheritance could only happen on the
+		 * listen(2) sockets with SO_REUSEPORT_LB set.
+		 */
+		inp_inh = in_pcblookup_lbgroup_last(inp);
+	}
+
 #ifdef TCP_OFFLOAD
 	if (tp->t_state == TCPS_LISTEN)
 		tcp_offload_listen_stop(tp);
@@ -1658,7 +1676,16 @@
 		tcp_state_change(tp, TCPS_CLOSED);
 	KASSERT(inp->inp_socket != NULL, ("tcp_close: inp_socket NULL"));
 	so = inp->inp_socket;
+
 	soisdisconnected(so);
+
+	if(listen)
+	{
+		if(inp_inh != NULL && inp_inh->inp_socket != NULL) {
+			soinherit(so, inp_inh->inp_socket);
+		}
+	}
+
 	if (inp->inp_flags & INP_SOCKREF) {
 		KASSERT(so->so_state & SS_PROTOREF,
 		    ("tcp_close: !SS_PROTOREF"));
Index: sys/netinet/tcp_syncache.c
===================================================================
--- sys/netinet/tcp_syncache.c
+++ sys/netinet/tcp_syncache.c
@@ -838,7 +838,7 @@
 	if (V_functions_inherit_listen_socket_stack && blk != tp->t_fb) {
 		/*
 		 * Our parents t_fb was not the default,
-		 * we need to release our ref on tp->t_fb and 
+		 * we need to release our ref on tp->t_fb and
 		 * pickup one on the new entry.
 		 */
 		struct tcp_function_block *rblk;
Index: sys/netinet6/ip6_output.c
===================================================================
--- sys/netinet6/ip6_output.c
+++ sys/netinet6/ip6_output.c
@@ -1452,6 +1452,15 @@
 				INP_WUNLOCK(in6p);
 				error = 0;
 				break;
+			case SO_REUSEPORT_LB:
+				INP_WLOCK(in6p);
+				if ((so->so_options & SO_REUSEPORT_LB) != 0)
+					in6p->inp_flags2 |= INP_REUSEPORT_LB;
+				else
+					in6p->inp_flags2 &= ~INP_REUSEPORT_LB;
+				INP_WUNLOCK(in6p);
+				error = 0;
+				break;
 			case SO_SETFIB:
 				INP_WLOCK(in6p);
 				in6p->inp_inc.inc_fibnum = so->so_fibnum;
Index: sys/sys/socket.h
===================================================================
--- sys/sys/socket.h
+++ sys/sys/socket.h
@@ -145,6 +145,9 @@
 #define	SO_NO_OFFLOAD	0x4000		/* socket cannot be offloaded */
 #define	SO_NO_DDP	0x8000		/* disable direct data placement */
 
+// XXX: so_options was only 16 bit, now globally increased to 32 bit
+#define	SO_REUSEPORT_LB	0x00010000 /* reuse with load balancing */
+
 /*
  * Additional options, not kept in so_options.
  */
Index: sys/sys/socketvar.h
===================================================================
--- sys/sys/socketvar.h
+++ sys/sys/socketvar.h
@@ -78,7 +78,7 @@
 	struct selinfo	so_rdsel;	/* (b/cr) for so_rcv/so_comp */
 	struct selinfo	so_wrsel;	/* (b/cs) for so_snd */
 	short	so_type;		/* (a) generic type, see socket.h */
-	short	so_options;		/* (b) from socket call, see socket.h */
+    int		so_options;		/* (b) from socket call, see socket.h */
 	short	so_linger;		/* time to linger close(2) */
 	short	so_state;		/* (b) internal state flags SS_* */
 	void	*so_pcb;		/* protocol control block */
@@ -200,7 +200,7 @@
 	size_t	xso_len;	/* length of this structure */
 	struct	socket *xso_so;	/* makes a convenient handle sometimes */
 	short	so_type;
-	short	so_options;
+	int		so_options;
 	short	so_linger;
 	short	so_state;
 	caddr_t	so_pcb;		/* another convenient handle */
@@ -386,6 +386,7 @@
 int	sodisconnect(struct socket *so);
 struct	sockaddr *sodupsockaddr(const struct sockaddr *sa, int mflags);
 void	sofree(struct socket *so);
+void	soinherit(struct socket *so, struct socket *so_inh);
 void	sohasoutofband(struct socket *so);
 int	solisten(struct socket *so, int backlog, struct thread *td);
 void	solisten_proto(struct socket *so, int backlog);