net/smc: improve return codes for SMC-Dv2

To allow better problem diagnosis the return codes for SMC-Dv2 are
improved by this patch. A few more CLC DECLINE codes are defined and
sent to the peer when an SMC connection cannot be established.
There are now multiple SMC variations that are offered by the client and
the server may encounter problems to initialize all of them.
Because only one diagnosis code can be sent to the client the decision
was made to send the first code that was encountered. Because the server
tries the variations in the order of importance (SMC-Dv2, SMC-D, SMC-R)
this makes sure that the diagnosis code of the most important variation
is sent.

v2: initialize rc in smc_listen_v2_check().

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Link: https://lore.kernel.org/r/20201031181938.69903-1-kgraul@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 41 insertions, 20 deletions

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index e9f487c8c6d5..527185af7bf3 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1346,6 +1346,7 @@ static int smc_listen_v2_check(struct smc_sock *new_smc,
 {
 	struct smc_clc_smcd_v2_extension *pclc_smcd_v2_ext;
 	struct smc_clc_v2_extension *pclc_v2_ext;
+	int rc = SMC_CLC_DECL_PEERNOSMC;
 
 	ini->smc_type_v1 = pclc->hdr.typev1;
 	ini->smc_type_v2 = pclc->hdr.typev2;
@@ -1353,29 +1354,30 @@ static int smc_listen_v2_check(struct smc_sock *new_smc,
 	if (pclc->hdr.version > SMC_V1)
 		ini->smcd_version |=
 				ini->smc_type_v2 != SMC_TYPE_N ? SMC_V2 : 0;
+	if (!(ini->smcd_version & SMC_V2)) {
+		rc = SMC_CLC_DECL_PEERNOSMC;
+		goto out;
+	}
 	if (!smc_ism_v2_capable) {
 		ini->smcd_version &= ~SMC_V2;
+		rc = SMC_CLC_DECL_NOISM2SUPP;
 		goto out;
 	}
 	pclc_v2_ext = smc_get_clc_v2_ext(pclc);
 	if (!pclc_v2_ext) {
 		ini->smcd_version &= ~SMC_V2;
+		rc = SMC_CLC_DECL_NOV2EXT;
 		goto out;
 	}
 	pclc_smcd_v2_ext = smc_get_clc_smcd_v2_ext(pclc_v2_ext);
-	if (!pclc_smcd_v2_ext)
+	if (!pclc_smcd_v2_ext) {
 		ini->smcd_version &= ~SMC_V2;
+		rc = SMC_CLC_DECL_NOV2DEXT;
+	}
 
 out:
-	if (!ini->smcd_version) {
-		if (pclc->hdr.typev1 == SMC_TYPE_B ||
-		    pclc->hdr.typev2 == SMC_TYPE_B)
-			return SMC_CLC_DECL_NOSMCDEV;
-		if (pclc->hdr.typev1 == SMC_TYPE_D ||
-		    pclc->hdr.typev2 == SMC_TYPE_D)
-			return SMC_CLC_DECL_NOSMCDDEV;
-		return SMC_CLC_DECL_NOSMCRDEV;
-	}
+	if (!ini->smcd_version)
+		return rc;
 
 	return 0;
 }
@@ -1473,6 +1475,12 @@ static void smc_check_ism_v2_match(struct smc_init_info *ini,
 	}
 }
 
+static void smc_find_ism_store_rc(u32 rc, struct smc_init_info *ini)
+{
+	if (!ini->rc)
+		ini->rc = rc;
+}
+
 static void smc_find_ism_v2_device_serv(struct smc_sock *new_smc,
 					struct smc_clc_msg_proposal *pclc,
 					struct smc_init_info *ini)
@@ -1483,7 +1491,7 @@ static void smc_find_ism_v2_device_serv(struct smc_sock *new_smc,
 	unsigned int matches = 0;
 	u8 smcd_version;
 	u8 *eid = NULL;
-	int i;
+	int i, rc;
 
 	if (!(ini->smcd_version & SMC_V2) || !smcd_indicated(ini->smc_type_v2))
 		goto not_found;
@@ -1492,8 +1500,10 @@ static void smc_find_ism_v2_device_serv(struct smc_sock *new_smc,
 	smc_v2_ext = smc_get_clc_v2_ext(pclc);
 	smcd_v2_ext = smc_get_clc_smcd_v2_ext(smc_v2_ext);
 	if (!smcd_v2_ext ||
-	    !smc_v2_ext->hdr.flag.seid) /* no system EID support for SMCD */
+	    !smc_v2_ext->hdr.flag.seid) { /* no system EID support for SMCD */
+		smc_find_ism_store_rc(SMC_CLC_DECL_NOSEID, ini);
 		goto not_found;
+	}
 
 	mutex_lock(&smcd_dev_list.mutex);
 	if (pclc_smcd->ism.chid)
@@ -1525,9 +1535,12 @@ static void smc_find_ism_v2_device_serv(struct smc_sock *new_smc,
 		ini->smcd_version = SMC_V2;
 		ini->is_smcd = true;
 		ini->ism_selected = i;
-		if (smc_listen_ism_init(new_smc, ini))
+		rc = smc_listen_ism_init(new_smc, ini);
+		if (rc) {
+			smc_find_ism_store_rc(rc, ini);
 			/* try next active ISM device */
 			continue;
+		}
 		return; /* matching and usable V2 ISM device found */
 	}
 	/* no V2 ISM device could be initialized */
@@ -1544,19 +1557,23 @@ static void smc_find_ism_v1_device_serv(struct smc_sock *new_smc,
 					struct smc_init_info *ini)
 {
 	struct smc_clc_msg_smcd *pclc_smcd = smc_get_clc_msg_smcd(pclc);
+	int rc = 0;
 
 	/* check if ISM V1 is available */
 	if (!(ini->smcd_version & SMC_V1) || !smcd_indicated(ini->smc_type_v1))
 		goto not_found;
 	ini->is_smcd = true; /* prepare ISM check */
 	ini->ism_peer_gid[0] = ntohll(pclc_smcd->ism.gid);
-	if (smc_find_ism_device(new_smc, ini))
+	rc = smc_find_ism_device(new_smc, ini);
+	if (rc)
 		goto not_found;
 	ini->ism_selected = 0;
-	if (!smc_listen_ism_init(new_smc, ini))
+	rc = smc_listen_ism_init(new_smc, ini);
+	if (!rc)
 		return;		/* V1 ISM device found */
 
 not_found:
+	smc_find_ism_store_rc(rc, ini);
 	ini->ism_dev[0] = NULL;
 	ini->is_smcd = false;
 }
@@ -1613,16 +1630,16 @@ static int smc_listen_find_device(struct smc_sock *new_smc,
 		return 0;
 
 	if (!(ini->smcd_version & SMC_V1))
-		return SMC_CLC_DECL_NOSMCDEV;
+		return ini->rc ?: SMC_CLC_DECL_NOSMCD2DEV;
 
 	/* check for matching IP prefix and subnet length */
 	rc = smc_listen_prfx_check(new_smc, pclc);
 	if (rc)
-		return rc;
+		return ini->rc ?: rc;
 
 	/* get vlan id from IP device */
 	if (smc_vlan_by_tcpsk(new_smc->clcsock, ini))
-		return SMC_CLC_DECL_GETVLANERR;
+		return ini->rc ?: SMC_CLC_DECL_GETVLANERR;
 
 	/* check for ISM device matching V1 proposed device */
 	smc_find_ism_v1_device_serv(new_smc, pclc, ini);
@@ -1630,10 +1647,14 @@ static int smc_listen_find_device(struct smc_sock *new_smc,
 		return 0;
 
 	if (pclc->hdr.typev1 == SMC_TYPE_D)
-		return SMC_CLC_DECL_NOSMCDDEV; /* skip RDMA and decline */
+		/* skip RDMA and decline */
+		return ini->rc ?: SMC_CLC_DECL_NOSMCDDEV;
 
 	/* check if RDMA is available */
-	return smc_find_rdma_v1_device_serv(new_smc, pclc, ini);
+	rc = smc_find_rdma_v1_device_serv(new_smc, pclc, ini);
+	smc_find_ism_store_rc(rc, ini);
+
+	return (!rc) ? 0 : ini->rc;
 }
 
 /* listen worker: finish RDMA setup */