From 3b4ca6b87dae6b11da137b6afb4cf8275687d281 Mon Sep 17 00:00:00 2001

From: Chris Leech <cleech@redhat.com>

Date: Thu, 24 Jan 2019 18:16:47 -0800

Subject: [PATCH] fcoemon: netlink buffer resize fix

The recv buffer resizing for netlink messages looks to have always been

busted, it discards some of the data in the process of increasing the

buffer size.

I've recently seen issues where the size of the netlink attributes in a

GETLINK request hit the fcm_link_buf_size window and some of the network

interfaces were ignored by fcoemon (happened mostly with recent kernels,

2 dual-port bnx2 NICs, bonding for LAN traffic on 2 ports and FCoE on

the other 2).  When the ignored interface happens to be the one you want

to use for FCoE, it never gets fixed.

This fixes the buffer resize code to use MSG_PEEK|MSG_TRUNC to check for

the needed buffer size first, and then resize with realloc when needed.

This might not actually be needed, with an 8k buffer I don't think the

kernel side will send more at once until after it sees the application

post a larger buffer, but I did force a resize and see that it worked.

Signed-off-by: Chris Leech <cleech@redhat.com>

---

 fcoemon.c | 54 ++++++++++++++++++------------------------------------

 1 file changed, 18 insertions(+), 36 deletions(-)

diff --git a/fcoemon.c b/fcoemon.c

index 9a400c56b72..9af0f1284af 100644

--- a/fcoemon.c

+++ b/fcoemon.c

@@ -328,7 +328,6 @@ static int fcm_link_socket;

 static int fcm_link_seq;

 static void fcm_link_recv(void *);

 static void fcm_link_getlink(void);

-static int fcm_link_buf_check(size_t);

 static void clear_dcbd_info(struct fcm_netif *ff);

 static int fcoe_vid_from_ifname(const char *ifname);

@@ -354,8 +353,7 @@ char progname[20];

  * large enough to fit and expand it if we ever do a read that almost fills it.

  */

 static char *fcm_link_buf;

-static size_t fcm_link_buf_size = 4096;	/* initial size */

-static const size_t fcm_link_buf_fuzz = 300;	/* "almost full" remainder */

+static size_t fcm_link_buf_size = 8192;	/* initial size */

 /*

  * A value must be surrounded by quates, e.g. "x".

@@ -1848,8 +1846,22 @@ static void fcm_link_recv(UNUSED void *arg)

 	size_t plen;

 	size_t rlen;

+	/* check to make sure our receive buffer is large enough,

+	 * or scale it up as needed */

+	rc = recv(fcm_link_socket, NULL, 0, MSG_PEEK | MSG_TRUNC);

+	if (rc > fcm_link_buf_size) {

+		FCM_LOG_DBG("resizing link buf to %d bytes\n", rc);

+		void *resize = realloc(fcm_link_buf, rc);

+		if (resize) {

+			fcm_link_buf = resize;

+			fcm_link_buf_size = rc;

+		} else {

+			FCM_LOG_ERR(errno, "Failed to allocate link buffer");

+		}

+	}

+

 	buf = fcm_link_buf;

-	rc = read(fcm_link_socket, buf, fcm_link_buf_size);

+	rc = recv(fcm_link_socket, buf, fcm_link_buf_size, 0);

 	if (rc <= 0) {

 		if (rc < 0)

 			FCM_LOG_ERR(errno, "Error reading from "

@@ -1858,11 +1870,6 @@ static void fcm_link_recv(UNUSED void *arg)

 		return;

 	}

-	if (fcm_link_buf_check(rc)) {

-		fcm_link_getlink();

-		return;

-	}

-

 	hp = (struct nlmsghdr *)buf;

 	rlen = rc;

 	for (hp = (struct nlmsghdr *)buf; NLMSG_OK(hp, rlen);

@@ -1927,34 +1934,9 @@ static void fcm_link_getlink(void)

 	msg.nl.nlmsg_pid = getpid();

 	msg.ifi.ifi_family = AF_UNSPEC;

 	msg.ifi.ifi_type = ARPHRD_ETHER;

-	rc = write(fcm_link_socket, &msg, sizeof(msg));

+	rc = send(fcm_link_socket, &msg, sizeof(msg), 0);

 	if (rc < 0)

-		FCM_LOG_ERR(errno, "write error");

-}

-

-/*

- * Check for whether buffer needs to grow based on amount read.

- * Free's the old buffer so don't use that after this returns non-zero.

- */

-static int fcm_link_buf_check(size_t read_len)

-{

-	char *buf;

-	size_t len = read_len;

-

-	if (len > fcm_link_buf_size - fcm_link_buf_fuzz) {

-		len = fcm_link_buf_size;

-		len = len + len / 2;	/* grow by 50% */

-		buf = malloc(len);

-		if (buf != NULL) {

-			free(fcm_link_buf);

-			fcm_link_buf = buf;

-			fcm_link_buf_size = len;

-			return 1;

-		} else {

-			FCM_LOG_ERR(errno, "failed to allocate link buffer");

-		}

-	}

-	return 0;

+		FCM_LOG_ERR(errno, "send error");

 }

 static void fcm_fcoe_init(void)

-- 

2.21.0