From aa6a96ba78bacb2792f2a6c26b6873b3ff4e35b8 Mon Sep 17 00:00:00 2001
From: Pat Ruddy <pat@voltanet.io>
Date: Wed, 3 Mar 2021 11:59:30 +0000
Subject: [PATCH] ospf6d: read ospf6 socket until failure

To ensure we read all the datagrams availabe from a socket when the
read task is scheduled, make the read helper return and error or
continue enum and loop unitl an error is received.
This requires the read from the socket to be non blocking

Signed-off-by: Pat Ruddy <pat@voltanet.io>
---
 ospf6d/ospf6_message.c | 35 +++++++++++++++++++++++++++--------
 ospf6d/ospf6_network.c | 11 +++++++----
 2 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/ospf6d/ospf6_message.c b/ospf6d/ospf6_message.c
index 1afcf78a8f..e6d09b9a08 100644
--- a/ospf6d/ospf6_message.c
+++ b/ospf6d/ospf6_message.c
@@ -1572,9 +1572,14 @@ void ospf6_message_terminate(void)
 	iobuflen = 0;
 }
 
+enum ospf6_read_return_enum {
+	OSPF6_READ_ERROR,
+	OSPF6_READ_CONTINUE,
+};
+
 static int ospf6_read_helper(int sockfd, struct ospf6 *ospf6)
 {
-	unsigned int len;
+	int len;
 	struct in6_addr src, dst;
 	ifindex_t ifindex;
 	struct iovec iovector[2];
@@ -1593,9 +1598,12 @@ static int ospf6_read_helper(int sockfd, struct ospf6 *ospf6)
 
 	/* receive message */
 	len = ospf6_recvmsg(&src, &dst, &ifindex, iovector, sockfd);
-	if (len > iobuflen) {
+	if (len < 0)
+		return OSPF6_READ_ERROR;
+
+	if ((uint)len > iobuflen) {
 		flog_err(EC_LIB_DEVELOPMENT, "Excess message read");
-		return 0;
+		return OSPF6_READ_ERROR;
 	}
 
 	oi = ospf6_interface_lookup_by_ifindex(ifindex, ospf6->vrf_id);
@@ -1604,19 +1612,19 @@ static int ospf6_read_helper(int sockfd, struct ospf6 *ospf6)
 		if (IS_OSPF6_DEBUG_MESSAGE(OSPF6_MESSAGE_TYPE_UNKNOWN,
 					   RECV_HDR))
 			zlog_debug("Message received on disabled interface");
-		return 0;
+		return OSPF6_READ_CONTINUE;
 	}
 	if (CHECK_FLAG(oi->flag, OSPF6_INTERFACE_PASSIVE)) {
 		if (IS_OSPF6_DEBUG_MESSAGE(OSPF6_MESSAGE_TYPE_UNKNOWN,
 					   RECV_HDR))
 			zlog_debug("%s: Ignore message on passive interface %s",
 				   __func__, oi->interface->name);
-		return 0;
+		return OSPF6_READ_CONTINUE;
 	}
 
 	oh = (struct ospf6_header *)recvbuf;
 	if (ospf6_rxpacket_examin(oi, oh, len) != MSG_OK)
-		return 0;
+		return OSPF6_READ_CONTINUE;
 
 	/* Being here means, that no sizing/alignment issues were detected in
 	   the input packet. This renders the additional checks performed below
@@ -1677,13 +1685,14 @@ static int ospf6_read_helper(int sockfd, struct ospf6 *ospf6)
 		assert(0);
 	}
 
-	return 0;
+	return OSPF6_READ_CONTINUE;
 }
 
 int ospf6_receive(struct thread *thread)
 {
 	int sockfd;
 	struct ospf6 *ospf6;
+	int count = 0;
 
 	/* add next read thread */
 	ospf6 = THREAD_ARG(thread);
@@ -1692,7 +1701,17 @@ int ospf6_receive(struct thread *thread)
 	thread_add_read(master, ospf6_receive, ospf6, ospf6->fd,
 			&ospf6->t_ospf6_receive);
 
-	return ospf6_read_helper(sockfd, ospf6);
+	while (count < 20) {
+		count++;
+		switch (ospf6_read_helper(sockfd, ospf6)) {
+		case OSPF6_READ_ERROR:
+			return 0;
+		case OSPF6_READ_CONTINUE:
+			break;
+		}
+	}
+
+	return 0;
 }
 
 static void ospf6_send(struct in6_addr *src, struct in6_addr *dst,
diff --git a/ospf6d/ospf6_network.c b/ospf6d/ospf6_network.c
index 76f98fecdd..5961cfe66a 100644
--- a/ospf6d/ospf6_network.c
+++ b/ospf6d/ospf6_network.c
@@ -257,10 +257,13 @@ int ospf6_recvmsg(struct in6_addr *src, struct in6_addr *dst,
 	rmsghdr.msg_control = (caddr_t)cmsgbuf;
 	rmsghdr.msg_controllen = sizeof(cmsgbuf);
 
-	retval = recvmsg(ospf6_sock, &rmsghdr, 0);
-	if (retval < 0)
-		zlog_warn("recvmsg failed: %s", safe_strerror(errno));
-	else if (retval == iov_totallen(message))
+	retval = recvmsg(ospf6_sock, &rmsghdr, MSG_DONTWAIT);
+	if (retval < 0) {
+		if (errno != EAGAIN && errno != EWOULDBLOCK)
+			zlog_warn("stream_recvmsg failed: %s",
+				  safe_strerror(errno));
+		return retval;
+	} else if (retval == iov_totallen(message))
 		zlog_warn("recvmsg read full buffer size: %d", retval);
 
 	/* source address */