Index: share/man/man4/divert.4
===================================================================
--- share/man/man4/divert.4
+++ share/man/man4/divert.4
@@ -155,6 +155,23 @@
 .Pp
 Binding to port numbers less than 1024 requires super-user access, as does
 creating a socket of type SOCK_RAW.
+.Pp
+There are two options for
+.Xr setsockopt 2
+and
+.Xr getsockopt 2
+that can be used to set and get the send and receive buffer sizes.
+.Pp
+The options for send and receive are
+.Dv IP_DIVSENDBUF
+and
+.Dv IP_DIVRECVBUF
+respectively. As an example, to set these buffer sizes in a program:
+.Bd -literal
+unsigned long sndbuf = 8192, rcvbuf = 16384;
+setsockopt(s, IPPROTO_DIVERT, IP_DIVSENDBUF, &sndbuf, sizeof(sndbuf));
+setsockopt(s, IPPROTO_DIVERT, IP_DIVRECVBUF, &rcvbuf, sizeof(rcvbuf));
+.Ed
 .Sh ERRORS
 Writing to a divert socket can return these errors, along with
 the usual errors possible when writing raw packets:
Index: sys/netinet/in.h
===================================================================
--- sys/netinet/in.h
+++ sys/netinet/in.h
@@ -498,6 +498,10 @@
 #define	IP_RECVFLOWID		93   /* bool; receive IP flowid/flowtype w/ datagram */
 #define	IP_RECVRSSBUCKETID	94   /* bool; receive IP RSS bucket id w/ datagram */
 
+/* Divert definitions */
+#define IP_DIVSENDBUF		95	/* u_long; send divert buffer size */
+#define IP_DIVRECVBUF		96	/* u_long; receive divert buffer size */
+
 /*
  * Defaults and limits for options
  */
Index: sys/netinet/ip_divert.c
===================================================================
--- sys/netinet/ip_divert.c
+++ sys/netinet/ip_divert.c
@@ -561,6 +561,7 @@
 {
 	struct inpcb *inp;
 	int error;
+	u_long sendspace, recvspace;
 
 	inp  = sotoinpcb(so);
 	KASSERT(inp == NULL, ("div_attach: inp != NULL"));
@@ -569,7 +570,9 @@
 		if (error)
 			return (error);
 	}
-	error = soreserve(so, div_sendspace, div_recvspace);
+	sendspace = so->divsendspace ? so->divsendspace : div_sendspace;
+	recvspace = so->divrecvspace ? so->divrecvspace : div_recvspace;
+	error = soreserve(so, sendspace, recvspace);
 	if (error)
 		return error;
 	INP_INFO_WLOCK(&V_divcbinfo);
Index: sys/netinet/raw_ip.c
===================================================================
--- sys/netinet/raw_ip.c
+++ sys/netinet/raw_ip.c
@@ -660,6 +660,15 @@
 				error = ENOPROTOOPT;
 			break ;
 
+		case IP_DIVSENDBUF:
+			optval = so->divsendspace;
+			error = sooptcopyout(sopt, &optval, sizeof optval);
+			break;
+		case IP_DIVRECVBUF:
+			optval = so->divrecvspace;
+			error = sooptcopyout(sopt, &optval, sizeof optval);
+			break;
+
 		case MRT_INIT:
 		case MRT_DONE:
 		case MRT_ADD_VIF:
@@ -746,6 +755,21 @@
 				return (error);
 			error = ip_rsvp_vif ?
 				ip_rsvp_vif(so, sopt) : EINVAL;
+			break;
+
+		case IP_DIVSENDBUF:
+			error = sooptcopyin(sopt, &optval, sizeof optval,
+					    sizeof optval);
+			if (error)
+				break;
+			so->divsendspace = optval;
+			break;
+		case IP_DIVRECVBUF:
+			error = sooptcopyin(sopt, &optval, sizeof optval,
+					    sizeof optval);
+			if (error)
+				break;
+			so->divrecvspace = optval;
 			break;
 
 		case MRT_INIT:
Index: sys/sys/socketvar.h
===================================================================
--- sys/sys/socketvar.h
+++ sys/sys/socketvar.h
@@ -102,6 +102,9 @@
 	void	*so_emuldata;		/* (b) private data for emulators */
 	so_dtor_t *so_dtor;		/* (b) optional destructor */
 	struct	osd	osd;		/* Object Specific extensions */
+	/* divert socket buffer sizes */
+	u_long divsendspace;		/* divert send buffer size */
+	u_long divrecvspace;		/* divert receive buffer size */
 	/*
 	 * so_fibnum, so_user_cookie and friends can be used to attach
 	 * some user-specified metadata to a socket, which then can be