caif: Use common error handling code in cfdgml_receive()

From: Markus Elfring <[email protected]>
Date: Tue, 7 Nov 2017 11:30:25 +0100

* Adjust jump targets so that a bit of exception handling can be better reused at the end of this function.

* Adjust two condition checks.

This issue was detected by using the Coccinelle software.

---

v1 - Request for comments:
I can offer another bit of information for a software development discussion. 💭

The affected source file can be compiled for the processor architecture “x86_64� by a tool like “GCC 6.4.1+r251631-1.3� from the software distribution “openSUSE Tumbleweed� with the following command example.

my_cc=/usr/bin/gcc-6 \
&& my_module=net/caif/cfdgml.o \
&& for XYZ in 0 s 3; do echo " _____ $XYZ _____" \
&& my_extra="-O$XYZ" \
&& git checkout next-20171102 \
&& make -j4 CC="${my_cc}" HOSTCC="${my_cc}" EXTRA_CFLAGS="${my_extra}" allmodconfig "${my_module}" \
&& size "${my_module}" \
&& git checkout ':/^caif: Use common error handling code in cfdgml_receive' \
&& make -j4 CC="${my_cc}" HOSTCC="${my_cc}" EXTRA_CFLAGS="${my_extra}" allmodconfig "${my_module}" \
&& size "${my_module}"; done

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║   O0    │ -59  ║
║   Os    │ +24  ║
║   O3    │ +36  ║

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 net/caif/cfdgml.c | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

index 3bdddb32d55a..cc7b2c944bb2 100644
@@ -47,18 +47,13 @@ static int cfdgml_receive(struct cflayer *layr, struct cfpkt *pkt)
 	caif_assert(layr->receive != NULL);
 	caif_assert(layr->ctrlcmd != NULL);
 
-	if (cfpkt_extr_head(pkt, &cmd, 1) < 0) {
-		pr_err("Packet is erroneous!\n");
-		cfpkt_destroy(pkt);
-		return -EPROTO;
-	}
+	if (cfpkt_extr_head(pkt, &cmd, 1))
+		goto report_packet_failure;
 
 	if ((cmd & DGM_CMD_BIT) = 0) {
-		if (cfpkt_extr_head(pkt, &dgmhdr, 3) < 0) {
-			pr_err("Packet is erroneous!\n");
-			cfpkt_destroy(pkt);
-			return -EPROTO;
-		}
+		if (cfpkt_extr_head(pkt, &dgmhdr, 3))
+			goto report_packet_failure;
+
 		ret = layr->up->receive(layr->up, pkt);
 		return ret;
 	}

@@ -66,17 +61,23 @@ static int cfdgml_receive(struct cflayer *layr, struct cfpkt *pkt)
 	switch (cmd) {
 	case DGM_FLOW_OFF:	/* FLOW OFF */
 		layr->ctrlcmd(layr, CAIF_CTRLCMD_FLOW_OFF_IND, 0);
-		cfpkt_destroy(pkt);
-		return 0;
+		ret = 0;
+		goto destroy_packet;
 	case DGM_FLOW_ON:	/* FLOW ON */
 		layr->ctrlcmd(layr, CAIF_CTRLCMD_FLOW_ON_IND, 0);
-		cfpkt_destroy(pkt);
-		return 0;
+		ret = 0;
+		goto destroy_packet;
 	default:
-		cfpkt_destroy(pkt);
 		pr_info("Unknown datagram control %d (0x%x)\n", cmd, cmd);
-		return -EPROTO;
+		goto e_proto;
 	}
+report_packet_failure:
+	pr_err("Packet is erroneous!\n");
+e_proto:
+	ret = -EPROTO;
+destroy_packet:
+	cfpkt_destroy(pkt);
+	return ret;
 }
 
 static int cfdgml_transmit(struct cflayer *layr, struct cfpkt *pkt)

2.15.0

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