tcp: Make error handling in tcp_usr_send() more consistent

- Free the input mbuf in a single place instead of in every error path.
- Handle PRUS_NOTREADY consistently.
- Flush the socket's send buffer if an implicit connect fails.  At that
  point the mbuf has already been enqueued but we don't want to keep it
  in the send buffer.

Reviewed by:	gallatin, tuexen
Discussed with:	jhb
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D30349

1 files changed, 26 insertions, 41 deletions

diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
index 693cf553de44..37bedc0125c9 100644
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -993,13 +993,6 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 	if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
 		if (control)
 			m_freem(control);
-
-		/*
-		 * In case of PRUS_NOTREADY, tcp_usr_ready() is responsible
-		 * for freeing memory.
-		 */
-		if ((flags & PRUS_NOTREADY) == 0)
-			m_freem(m);
 		error = ECONNRESET;
 		goto out;
 	}
@@ -1007,7 +1000,6 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 		/* TCP doesn't do control messages (rights, creds, etc) */
 		if (control->m_len) {
 			m_freem(control);
-			m_freem(m);
 			error = EINVAL;
 			goto out;
 		}
@@ -1015,13 +1007,10 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 		control = NULL;
 	}
 	tp = intotcpcb(inp);
-	if (flags & PRUS_OOB) {
-		if ((error = tcp_pru_options_support(tp, PRUS_OOB)) != 0) {
-			if ((flags & PRUS_NOTREADY) == 0)
-				m_freem(m);
-			goto out;
-		}
-	}
+	if ((flags & PRUS_OOB) != 0 &&
+	    (error = tcp_pru_options_support(tp, PRUS_OOB)) != 0)
+		goto out;
+
 	TCPDEBUG1();
 	if (nam != NULL && tp->t_state < TCPS_SYN_SENT) {
 		switch (nam->sa_family) {
@@ -1029,30 +1018,24 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 		case AF_INET:
 			sinp = (struct sockaddr_in *)nam;
 			if (sinp->sin_len != sizeof(struct sockaddr_in)) {
-				m_freem(m);
 				error = EINVAL;
 				goto out;
 			}
 			if ((inp->inp_vflag & INP_IPV6) != 0) {
-				m_freem(m);
 				error = EAFNOSUPPORT;
 				goto out;
 			}
 			if (IN_MULTICAST(ntohl(sinp->sin_addr.s_addr))) {
-				m_freem(m);
 				error = EAFNOSUPPORT;
 				goto out;
 			}
 			if (ntohl(sinp->sin_addr.s_addr) == INADDR_BROADCAST) {
-				m_freem(m);
 				error = EACCES;
 				goto out;
 			}
 			if ((error = prison_remote_ip4(td->td_ucred,
-			    &sinp->sin_addr))) {
-				m_freem(m);
+			    &sinp->sin_addr)))
 				goto out;
-			}
 #ifdef INET6
 			isipv6 = 0;
 #endif
@@ -1065,17 +1048,14 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 
 			sin6 = (struct sockaddr_in6 *)nam;
 			if (sin6->sin6_len != sizeof(*sin6)) {
-				m_freem(m);
 				error = EINVAL;
 				goto out;
 			}
 			if ((inp->inp_vflag & INP_IPV6PROTO) == 0) {
-				m_freem(m);
 				error = EAFNOSUPPORT;
 				goto out;
 			}
 			if (IN6_IS_ADDR_MULTICAST(&sin6->sin6_addr)) {
-				m_freem(m);
 				error = EAFNOSUPPORT;
 				goto out;
 			}
@@ -1083,12 +1063,10 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 #ifdef INET
 				if ((inp->inp_flags & IN6P_IPV6_V6ONLY) != 0) {
 					error = EINVAL;
-					m_freem(m);
 					goto out;
 				}
 				if ((inp->inp_vflag & INP_IPV4) == 0) {
 					error = EAFNOSUPPORT;
-					m_freem(m);
 					goto out;
 				}
 				restoreflags = true;
@@ -1098,23 +1076,18 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 				if (IN_MULTICAST(
 				    ntohl(sinp->sin_addr.s_addr))) {
 					error = EAFNOSUPPORT;
-					m_freem(m);
 					goto out;
 				}
 				if ((error = prison_remote_ip4(td->td_ucred,
-				    &sinp->sin_addr))) {
-					m_freem(m);
+				    &sinp->sin_addr)))
 					goto out;
-				}
 				isipv6 = 0;
 #else /* !INET */
 				error = EAFNOSUPPORT;
-				m_freem(m);
 				goto out;
 #endif /* INET */
 			} else {
 				if ((inp->inp_vflag & INP_IPV6) == 0) {
-					m_freem(m);
 					error = EAFNOSUPPORT;
 					goto out;
 				}
@@ -1122,23 +1095,21 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 				inp->inp_vflag &= ~INP_IPV4;
 				inp->inp_inc.inc_flags |= INC_ISIPV6;
 				if ((error = prison_remote_ip6(td->td_ucred,
-				    &sin6->sin6_addr))) {
-					m_freem(m);
+				    &sin6->sin6_addr)))
 					goto out;
-				}
 				isipv6 = 1;
 			}
 			break;
 		}
 #endif /* INET6 */
 		default:
-			m_freem(m);
 			error = EAFNOSUPPORT;
 			goto out;
 		}
 	}
 	if (!(flags & PRUS_OOB)) {
 		sbappendstream(&so->so_snd, m, flags);
+		m = NULL;
 		if (nam && tp->t_state < TCPS_SYN_SENT) {
 			/*
 			 * Do implied connect if not yet connected,
@@ -1164,8 +1135,11 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 			if (error == 0 || inp->inp_lport != 0)
 				restoreflags = false;
 
-			if (error)
+			if (error) {
+				/* m is freed if PRUS_NOTREADY is unset. */
+				sbflush(&so->so_snd);
 				goto out;
+			}
 			if (IS_FASTOPEN(tp->t_flags))
 				tcp_fastopen_connect(tp);
 			else {
@@ -1206,7 +1180,6 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 		SOCKBUF_LOCK(&so->so_snd);
 		if (sbspace(&so->so_snd) < -512) {
 			SOCKBUF_UNLOCK(&so->so_snd);
-			m_freem(m);
 			error = ENOBUFS;
 			goto out;
 		}
@@ -1220,6 +1193,7 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 		 */
 		sbappendstream_locked(&so->so_snd, m, flags);
 		SOCKBUF_UNLOCK(&so->so_snd);
+		m = NULL;
 		if (nam && tp->t_state < TCPS_SYN_SENT) {
 			/*
 			 * Do implied connect if not yet connected,
@@ -1251,13 +1225,16 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 			if (error == 0 || inp->inp_lport != 0)
 				restoreflags = false;
 
-			if (error)
+			if (error != 0) {
+				/* m is freed if PRUS_NOTREADY is unset. */
+				sbflush(&so->so_snd);
 				goto out;
+			}
 			tp->snd_wnd = TTCP_CLIENT_SND_WND;
 			tcp_mss(tp, -1);
 		}
 		tp->snd_up = tp->snd_una + sbavail(&so->so_snd);
-		if (!(flags & PRUS_NOTREADY)) {
+		if ((flags & PRUS_NOTREADY) == 0) {
 			tp->t_flags |= TF_FORCEDATA;
 			error = tp->t_fb->tfb_tcp_output(tp);
 			tp->t_flags &= ~TF_FORCEDATA;
@@ -1268,8 +1245,16 @@ tcp_usr_send(struct socket *so, int flags, struct mbuf *m,
 	    &inp->inp_socket->so_snd,
 	    TCP_LOG_USERSEND, error,
 	    0, NULL, false);
+
 out:
 	/*
+	 * In case of PRUS_NOTREADY, the caller or tcp_usr_ready() is
+	 * responsible for freeing memory.
+	 */
+	if (m != NULL && (flags & PRUS_NOTREADY) == 0)
+		m_freem(m);
+
+	/*
 	 * If the request was unsuccessful and we changed flags,
 	 * restore the original flags.
 	 */