server and client: created structures in common to store REST arguments

fixed a serious bug where ports used by VMs were not being marked as free again!
added more tests to validate script
bumped server version to 1.8.1
bumped client version to 1.8.1

src/client/cmdTemplate/templateCreate.go

 package cmdTemplate
 
 import (
+    "nexus-common/params"
     u "nexus-client/utils"
     g "nexus-client/globals"
     "github.com/google/uuid"
@@ -65,15 +66,8 @@ func (cmd *Create)makeRequestForID(vmID uuid.UUID, name, access string) (*resty.
     client := g.GetInstance().Client
     host := g.GetInstance().Host
 
-    type TemplateArgs struct {
-        VMID uuid.UUID
-        Name string
-        Access string
-    }
-
-    templateArgs := &TemplateArgs { vmID, name, access }
-
-    resp, err := client.R().SetBody(templateArgs).Post(host+"/templates/vm")
+    p := &params.TplCreate{ vmID, name, access }
+    resp, err := client.R().SetBody(p).Post(host+"/templates/vm")
     if err != nil {
         return nil, err
     }

src/client/cmdTemplate/templateEdit.go

@@ -3,6 +3,7 @@ package cmdTemplate
 import (
     "errors"
     "strings"
+    "nexus-common/params"
     u "nexus-client/utils"
     g "nexus-client/globals"
 )
@@ -11,11 +12,6 @@ type Edit struct {
     Name string
 }
 
-type templateEditParameters struct {
-    Name string
-    Access string
-}
-
 func (cmd *Edit)GetName() string {
     return cmd.Name
 }
@@ -49,13 +45,13 @@ func (cmd *Edit)Run(args []string) int {
         return 1
     }
 
-    templateParams, err := cmd.parseArgs(args[1:])
+    p, err := cmd.parseArgs(args[1:])
     if err != nil {
         u.PrintlnErr(err.Error())
         return 1
     }
 
-    if templateParams == nil {
+    if p == nil {
         cmd.PrintUsage()
         return 1
     }
@@ -63,7 +59,7 @@ func (cmd *Edit)Run(args []string) int {
     tplID := args[0]
     statusCode := 0
 
-    resp, err := client.R().SetBody(templateParams).Put(host+"/templates/"+tplID)
+    resp, err := client.R().SetBody(p).Put(host+"/templates/"+tplID)
     if err != nil {
         u.PrintlnErr("Failed editing template \""+tplID+"\": "+err.Error())
         statusCode = 1
@@ -79,8 +75,8 @@ func (cmd *Edit)Run(args []string) int {
     return statusCode
 }
 
-func (cmd *Edit)parseArgs(args []string) (*templateEditParameters, error) {
-    templateParams := &templateEditParameters {}
+func (cmd *Edit)parseArgs(args []string) (*params.TplCreate, error) {
+    p := &params.TplCreate{}
     atLeastOneArg := false
 
     getStringVal := func(s string, prefix string) string {
@@ -94,13 +90,13 @@ func (cmd *Edit)parseArgs(args []string) (*templateEditParameters, error) {
     for _, arg := range args {
         s := getStringVal(arg, "name=")
         if s != "" {
-            templateParams.Name = s
+            p.Name = s
             atLeastOneArg = true
             continue
         }
         s = getStringVal(arg, "access=")
         if s != "" {
-            templateParams.Access = s
+            p.Access = s
             atLeastOneArg = true
             continue
         }
@@ -108,7 +104,7 @@ func (cmd *Edit)parseArgs(args []string) (*templateEditParameters, error) {
     }
 
     if atLeastOneArg {
-        return templateParams, nil
+        return p, nil
     } else {
         return nil, nil
     }

src/client/cmdUser/userSetCaps.go

@@ -6,6 +6,7 @@ import (
     "errors"
     "strings"
     "encoding/csv"
+    "nexus-common/params"
     u "nexus-client/utils"
     g "nexus-client/globals"
 )
@@ -38,10 +39,6 @@ func (cmd *SetCaps)PrintUsage() {
     u.PrintlnErr(usage)
 }
 
-type capsArgs struct {
-    Caps map[string]int `json:"caps"  validate:"required"`
-}
-
 func (cmd *SetCaps)Run(args []string) int {
     argc := len(args)
     if argc < 1 {
@@ -88,7 +85,7 @@ func (cmd *SetCaps)Run(args []string) int {
                 continue
             }
 
-            userCaps := &capsArgs { make(map[string]int) }
+            userCaps := &params.UserSetCaps{ make(map[string]int) }
 
             capsStr := strings.TrimSpace(columns[1])
             if len(capsStr) > 0 {
@@ -114,10 +111,9 @@ func (cmd *SetCaps)Run(args []string) int {
         }
     } else {
         // Argument is an email address
-
         email := args[0]
 
-        userCaps := &capsArgs { make(map[string]int) }
+        userCaps := &params.UserSetCaps{ make(map[string]int) }
         for _, cap := range args[1:] {
             userCaps.Caps[cap] = 1
         }
@@ -133,7 +129,7 @@ func (cmd *SetCaps)Run(args []string) int {
     return statusCode
 }
 
-func (cmd *SetCaps)runRequest(email string, userCaps *capsArgs) error {
+func (cmd *SetCaps)runRequest(email string, userCaps *params.UserSetCaps) error {
     client := g.GetInstance().Client
     host := g.GetInstance().Host
 

src/client/cmdUser/userUpdatePwd.go

 package cmdUser
 
 import (
+    "nexus-common/params"
     u "nexus-client/utils"
     g "nexus-client/globals"
 )
@@ -64,13 +65,8 @@ func (cmd *UpdatePwd)Run(args []string) int {
     }
 
     pwdStr := string(newPwd)
-
-    type PwdArgs struct {
-        Pwd string
-    }
-
-    pwdArgs := &PwdArgs{pwdStr}
-    resp, err := client.R().SetBody(pwdArgs).Put(host+"/users/pwd")
+    p := &params.UserSetPwd{pwdStr}
+    resp, err := client.R().SetBody(p).Put(host+"/users/pwd")
     if err != nil {
         u.PrintlnErr("Error: "+err.Error())
         return 1

src/client/nexus-cli/go.mod

@@ -4,6 +4,8 @@ go 1.18
 
 replace nexus-common/caps => ../../common/caps
 
+replace nexus-common/params => ../../common/params
+
 replace nexus-common/vm => ../../common/vm
 
 replace nexus-common/template => ../../common/template
@@ -58,6 +60,7 @@ require (
 	nexus-client/exec v0.0.0-00010101000000-000000000000 // indirect
 	nexus-client/version v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/caps v0.0.0-00010101000000-000000000000 // indirect
+	nexus-common/params v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/template v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/utils v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/vm v0.0.0-00010101000000-000000000000 // indirect

src/client/nexus-cli/validate

@@ -6,11 +6,13 @@ nexus_cli="./nexus-cli"
 
 partial_name="exam 328a2d0eff08"
 full_name="live $partial_name"
-creds_file=creds.pdf
+creds_pdf_file=creds.pdf
+creds_csv_file=creds.csv
 
 del_gen_files () {
     find . -name "$full_name *.tar.gz" -delete
-    rm -f $creds_file
+    rm -f $creds_pdf_file
+    rm -f $creds_csv_file
 }
 
 cleanup () {
@@ -90,9 +92,14 @@ check "vmstart VMs"
 sleep 3
 OK
 
-echo "Generate credentials pdf..."
-$nexus_cli vmcred2pdf "$full_name" $creds_file
-check "vmcred2pdf"
+echo "Generate credentials to PDF..."
+$nexus_cli vmcreds2pdf "$full_name" $creds_pdf_file
+check "vmcreds2pdf"
+OK
+
+echo "Generate credentials to CSV..."
+$nexus_cli vmcreds2csv "$full_name" $creds_csv_file
+check "vmcreds2csv"
 OK
 
 echo "Kill students VMs..."
@@ -106,6 +113,18 @@ $nexus_cli vmexportdir "$full_name" /home
 check "vmexportdir"
 OK
 
+echo "Re-start students VMs with previous credentials..."
+$nexus_cli vmstartwithcreds $creds_csv_file
+check "vmstartwithcreds VMs"
+sleep 10
+OK
+
+echo "Kill students VMs..."
+$nexus_cli vmkill "$full_name"
+sleep 3
+check "vmkill VMs"
+OK
+
 echo "Delete students VMs..."
 $nexus_cli vmdel "$partial_name"
 check "vmdel VMs"

src/client/nexush/go.mod

@@ -4,6 +4,8 @@ go 1.18
 
 replace nexus-common/caps => ../../common/caps
 
+replace nexus-common/params => ../../common/params
+
 replace nexus-common/vm => ../../common/vm
 
 replace nexus-common/template => ../../common/template
@@ -60,6 +62,7 @@ require (
 	nexus-client/utils v0.0.0-00010101000000-000000000000 // indirect
 	nexus-client/version v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/caps v0.0.0-00010101000000-000000000000 // indirect
+	nexus-common/params v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/template v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/utils v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/vm v0.0.0-00010101000000-000000000000 // indirect

src/client/version/version.go

@@ -8,7 +8,7 @@ import (
 const (
     major  = 1
     minor  = 8
-    bugfix = 0
+    bugfix = 1
 )
 
 type Version struct {

src/common/params/go.mod

+module nexus-common/params
+
+go 1.18

src/common/params/templates.go

+package params
+
+import (
+	"github.com/google/uuid"
+)
+
+type TplCreate struct {
+	VMID uuid.UUID      `json:"vmID" validate:"required"`
+	Name string         `json:"name" validate:"required,min=2"`
+	Access string       `json:"access" validate:"required,min=4"`
+}
+
+type TplEdit struct {
+	Name   string       `json:"name"`
+	Access string       `json:"access"`
+}

src/common/params/users.go

+package params
+
+import (
+	"nexus-common/caps"
+)
+
+type UserSetCaps struct {
+	Caps caps.Capabilities
+}
+
+type UserSetPwd struct {
+	Pwd string `json:"pwd" validate:"required,min=8"`
+}

src/common/params/vms.go

+package params
+
+import (
+	"nexus-common/vm"
+	"nexus-common/caps"
+	"github.com/google/uuid"
+)
+
+type VMCreate struct {
+	Name string           `json:"name"       validate:"required,min=4,max=256"`
+	Cpus int              `json:"cpus"       validate:"required,gte=1,lte=16"`
+	Ram int               `json:"ram"        validate:"required,gte=512,lte=32768"`
+	Nic vm.NicType        `json:"nic"        validate:"required`
+	UsbDevs []string      `json:"usbDevs"    validate:"required`
+	TemplateID uuid.UUID  `json:"templateID" validate:"required"`
+}
+
+type VMStartWithCreds struct {
+	Port int              `json:"port"       validate:"required,gte=1100,lte=65535"`
+	Pwd string            `json:"pwd"        validate:"required,min=8,max=64"`
+}
+
+type VMEdit struct {
+	Name string           `json:"name"       validate:"required,min=4,max=256"`
+	Cpus int              `json:"cpus"       validate:"required,gte=1,lte=16"`
+	Ram int               `json:"ram"        validate:"required,gte=512,lte=32768"`
+	Nic vm.NicType        `json:"nic"        validate:"required`
+	UsbDevs []string      `json:"usbDevs"    validate:"required`
+}
+
+type VMAddAccess struct {
+	Access caps.Capabilities `json:"access"  validate:"required"`
+}
+
+type VMExportDir struct {
+	Dir string  `json:"dir"`
+}

src/server/go.mod

@@ -6,6 +6,8 @@ replace nexus-common/template => ../common/template
 
 replace nexus-common/vm => ../common/vm
 
+replace nexus-common/params => ../common/params
+
 replace nexus-common/caps => ../common/caps
 
 replace nexus-server/consts => ./consts
@@ -62,6 +64,7 @@ require (
 	golang.org/x/text v0.3.7 // indirect
 	golang.org/x/time v0.0.0-20201208040808-7e3f01d25324 // indirect
 	nexus-common/caps v0.0.0-00010101000000-000000000000 // indirect
+	nexus-common/params v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/template v0.0.0-00010101000000-000000000000 // indirect
 	nexus-common/vm v0.0.0-00010101000000-000000000000 // indirect
 	nexus-server/exec v0.0.0-00010101000000-000000000000 // indirect

src/server/router/routerTemplates.go

@@ -6,6 +6,7 @@ import (
     "net/http"
     "path/filepath"
     "nexus-common/caps"
+    "nexus-common/params"
     "nexus-server/vms"
     "nexus-server/paths"
     "nexus-server/users"
@@ -66,13 +67,8 @@ func (r *RouterTemplates)CreateTemplateFromVM(c echo.Context) error {
         return echo.NewHTTPError(http.StatusUnauthorized, msgInsufficientCaps)
     }
 
-    // Deserializes and validates the client's parameters.
-    type Parameters struct {
-        VMID uuid.UUID      `json:"vmID" validate:"required"`
-        Name string         `json:"name" validate:"required,min=2"`
-        Access string       `json:"access" validate:"required,min=4"`
-    }
-    p := new(Parameters)
+    // Deserializes and validates client's parameters.
+    p := new(params.TplCreate)
     if err := decodeJson(c, &p); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
@@ -243,14 +239,10 @@ func (r *RouterTemplates)EditTemplateByID(c echo.Context) error {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
 
-    // Deserializes and validates the client's parameters.
+    // Deserializes and validates client's parameters.
     // Given these parameters are optional, we can't use a validator on them.
     // Validation is performed in templates.EditTemplate() instead.
-    type Parameters struct {
-        Name   string          `json:"name"`
-        Access string          `json:"access"`
-    }
-    p := new(Parameters)
+    p := new(params.TplEdit)
 
     if user.HasCapability(caps.CAP_TPL_EDIT_ANY) {
         if err := decodeJson(c, &p); err != nil {

src/server/router/routerUsers.go

@@ -3,6 +3,7 @@ package router
 import (
     "net/http"
     "nexus-common/caps"
+    "nexus-common/params"
     "nexus-server/users"
     "nexus-server/utils"
     "github.com/labstack/echo/v4"
@@ -128,18 +129,14 @@ func (r *RouterUsers) SetUserCaps(c echo.Context) error {
         return echo.NewHTTPError(http.StatusUnauthorized, msgInsufficientCaps)
     }
 
-    // Deserializes and validates the client's parameters.
-    type Parameters struct {
-        Caps caps.Capabilities
-    }
-    params := &Parameters{make(caps.Capabilities)}
-
-    if err := decodeJson(c, &params); err != nil {
+    // Deserializes and validates client's parameters.
+    p := new(params.UserSetCaps)
+    if err := decodeJson(c, &p); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
 
     // Checks capabilities are valid.
-    if err := caps.ValidateUserCaps(params.Caps); err != nil {
+    if err := caps.ValidateUserCaps(p.Caps); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
 
@@ -150,7 +147,7 @@ func (r *RouterUsers) SetUserCaps(c echo.Context) error {
     }
 
     // Updates the user's capabilities.
-    userToUpdate.Caps = params.Caps
+    userToUpdate.Caps = p.Caps
 
     // Updates user and saves the new user file.
     if err = r.users.UpdateUser(&userToUpdate); err != nil {
@@ -163,19 +160,14 @@ func (r *RouterUsers) SetUserCaps(c echo.Context) error {
 // Update the logged user's password.
 // curl --cacert ca.pem -X PUT http://localhost:1077/users/pwd -H 'Content-Type: application/json' -d '{"pwd": "new_password"}' -H "Authorization: Bearer <AccessToken>"
 func (r *RouterUsers) SetUserPwd(c echo.Context) error {
-    // Deserializes the client's parameters.
-    type Parameters struct {
-        Pwd string `json:"pwd" validate:"required,min=8"`
-    }
-    params := &Parameters{}
-
-    // Deserializes the JSON body and checks its validity.
-    if err := decodeJson(c, &params); err != nil {
+    // Deserializes and validates client's parameters.
+    p := new(params.UserSetPwd)
+    if err := decodeJson(c, &p); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
 
     // Checks the new password is valid.
-    if err := validator.New().Struct(params); err != nil {
+    if err := validator.New().Struct(p); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
 
@@ -186,7 +178,7 @@ func (r *RouterUsers) SetUserPwd(c echo.Context) error {
     }
 
     // Hashes and udpates the user's password.
-    user.Pwd = utils.HashPassword(params.Pwd)
+    user.Pwd = utils.HashPassword(p.Pwd)
 
     // Updates user and saves the new user file.
     if err = r.users.UpdateUser(user); err != nil {

src/server/router/routerVMs.go

@@ -6,7 +6,7 @@ import (
     "net/http"
     "path/filepath"
     "nexus-common/caps"
-    vmc "nexus-common/vm"
+    "nexus-common/params"
     "nexus-server/vms"
     "nexus-server/users"
     "nexus-server/paths"
@@ -179,15 +179,7 @@ func (r *RouterVMs)CreateVM(c echo.Context) error {
     }
 
     // Deserializes and validates client's parameters.
-    type Parameters struct {
-        Name string           `json:"name"       validate:"required,min=4,max=256"`
-        Cpus int              `json:"cpus"       validate:"required,gte=1,lte=16"`
-        Ram int               `json:"ram"        validate:"required,gte=512,lte=32768"`
-        Nic vmc.NicType       `json:"nic"        validate:"required`
-        UsbDevs []string      `json:"usbDevs"    validate:"required`
-        TemplateID uuid.UUID  `json:"templateID" validate:"required"`
-    }
-    p := new(Parameters)
+    p := new(params.VMCreate)
     if err := decodeJson(c, &p); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
@@ -243,16 +235,12 @@ func (r *RouterVMs)StartVMWithCreds(c echo.Context) error {
     return r.performVMAction(c, caps.CAP_VM_START_ANY, caps.CAP_VM_START, func(c echo.Context, vm *vms.VM) error {
 
         // Deserializes and validates client's parameters.
-        type Parameters struct {
-            Port int              `json:"port"       validate:"required,gte=1100,lte=65535"`
-            Pwd string            `json:"pwd"        validate:"required,min=8,max=64"`
-        }
-        p := new(Parameters)
+        p := new(params.VMStartWithCreds)
         if err := decodeJson(c, &p); err != nil {
             return echo.NewHTTPError(http.StatusBadRequest, err.Error())
         }
 
-        if err := r.vms.StartVMWithCreds(vm.GetID(), p.Port, p.Pwd); err != nil {
+        if err := r.vms.StartVMWithCreds(vm.GetID(), p.Port, true, p.Pwd); err != nil {
             return echo.NewHTTPError(http.StatusBadRequest, err.Error())
         }
         return c.JSONPretty(http.StatusOK, jsonMsg("OK"), "    ")
@@ -308,17 +296,10 @@ func (r *RouterVMs)RebootVM(c echo.Context) error {
 // curl --cacert ca.pem -X PUT https://localhost:1077/vms/e41f3556-ca24-4658-bd79-8c85bd6bff59 -H 'Content-Type: application/json' -d '{"name":"Edited VM","cpus":1,"ram":2048,"nic":"user","usbDevs":["1307:0165","1234:abcd"]}' -H "Authorization: Bearer <AccessToken>"
 func (r *RouterVMs)EditVMByID(c echo.Context) error {
     return r.performVMAction(c, caps.CAP_VM_EDIT_ANY, caps.CAP_VM_EDIT, func(c echo.Context, vm *vms.VM) error {
-        // Deserializes and validates the client's parameters.
+        // Deserializes and validates client's parameters.
         // Given these parameters are optional, we can't use a validator on them.
         // Validation is performed in vm.EditVM() instead.
-        type Parameters struct {
-            Name string           `json:"name"       validate:"required,min=4,max=256"`
-            Cpus int              `json:"cpus"       validate:"required,gte=1,lte=16"`
-            Ram int               `json:"ram"        validate:"required,gte=512,lte=32768"`
-            Nic vmc.NicType       `json:"nic"        validate:"required`
-            UsbDevs []string      `json:"usbDevs"    validate:"required`
-        }
-        p := new(Parameters)
+        p := new(params.VMEdit)
         if err := decodeJson(c, &p); err != nil {
             return echo.NewHTTPError(http.StatusBadRequest, err.Error())
         }
@@ -368,19 +349,16 @@ func (r *RouterVMs)SetVMAccessForUser(c echo.Context) error {
         }
     }
 
-    // Deserializes and validates the client's parameters.
-    type Parameters struct {
-        Access caps.Capabilities `json:"access"  validate:"required"`
-    }
-    params := new(Parameters)
-    if err := decodeJson(c, &params); err != nil {
+    // Deserializes and validates client's parameters.
+    p := new(params.VMAddAccess)
+    if err := decodeJson(c, &p); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
-    if err := validator.New().Struct(params); err != nil {
+    if err := validator.New().Struct(p); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
 
-    if err = r.vms.SetVMAccess(vmID, user.Email, email, params.Access); err != nil {
+    if err = r.vms.SetVMAccess(vmID, user.Email, email, p.Access); err != nil {
         return echo.NewHTTPError(http.StatusBadRequest, err.Error())
     }
 
@@ -438,10 +416,7 @@ func (r *RouterVMs)DeleteVMAccessForUser(c echo.Context) error {
 func (r *RouterVMs)ExportVMDir(c echo.Context) error {
     return r.performVMAction(c, caps.CAP_VM_READFS_ANY, caps.CAP_VM_READFS, func(c echo.Context, vm *vms.VM) error {
         // Deserializes and validates the client's parameter.
-        type Parameters struct {
-            Dir string  `json:"dir"`
-        }
-        p := new(Parameters)
+        p := new(params.VMExportDir)
         if err := decodeJson(c, &p); err != nil {
             return echo.NewHTTPError(http.StatusBadRequest, err.Error())
         }

src/server/version/version.go

@@ -7,7 +7,7 @@ import (
 const (
     major  = 1
     minor  = 8
-    bugfix = 0
+    bugfix = 1
 )
 
 type Version struct {

src/server/vms/vms.go

@@ -90,6 +90,7 @@ func InitVMs() error {
 // Returns the list of serialized VMs for which VMKeeperFn returns true.
 func (vms *VMs)GetNetworkSerializedVMs(keepFn VMKeeperFn) []vm.VMNetworkSerialized {
     vms.rwlock.RLock()
+
     list := []vm.VMNetworkSerialized{}
     for _, vm := range vms.m {
         vm.mutex.Lock()
@@ -173,16 +174,12 @@ func (vms *VMs)AddVM(vm *VM) error {
 }
 
 // Starts a VM by its ID, using the specified port and password.
-func (vms *VMs)StartVMWithCreds(vmID uuid.UUID, port int, pwd string) error {
+// If checkPort is true, a check is performed on the specified port and if it is already
+// in use, the function fails and returns a corresponding error.
+func (vms *VMs)StartVMWithCreds(vmID uuid.UUID, port int, checkPort bool, pwd string) error {
     vms.rwlock.Lock()
     defer vms.rwlock.Unlock()
 
-    if vms.usedPorts[port] || !utils.IsPortAvailable(port) {
-        return errors.New("Failed starting VM: port already in use")
-    } else {
-        vms.usedPorts[port] = true
-    }
-
     vm, err := vms.getVMUnsafe(vmID)
     if err != nil {
         return err
@@ -195,8 +192,21 @@ func (vms *VMs)StartVMWithCreds(vmID uuid.UUID, port int, pwd string) error {
         return errors.New("Failed starting VM: VM already running")
     }
 
+    if checkPort {
+        if vms.usedPorts[port] {
+            return errors.New("Failed starting VM: port already in use")
+        } else if !utils.IsPortAvailable(port) {
+            return errors.New("Failed starting VM: port not available")
+        } else {
+            vms.usedPorts[port] = true
+        }
+    } else {
+        vms.usedPorts[port] = true
+    }
+
     totalRAM, availRAM, err := utils.GetRAM()
     if err != nil {
+        vms.usedPorts[port] = false
         return errors.New("Failed starting VM: failed obtaining memory info: "+err.Error())
     }
 
@@ -209,42 +219,51 @@ func (vms *VMs)StartVMWithCreds(vmID uuid.UUID, port int, pwd string) error {
     // otherwise, refuses to run it in order to avoid RAM saturation.
     if availRAM - vms.usedRAM <= int(math.Round(float64(totalRAM)*(1.-c.RamUsageLimit))) {
         vms.usedRAM -= estimatedVmRAM
+        vms.usedPorts[port] = false
         return errors.New("Failed starting VM: insufficient free RAM")
     }
 
     // This callback is called once the VM started with vm.start terminates.
     endofExecFn := func (vm *VM) {
+        vms.rwlock.Lock()
+        vms.usedPorts[port] = false
+        vms.usedRAM -= estimatedVmRAM
+        vms.rwlock.Unlock()
         vm.mutex.Lock()
         vm.removeSecretFile()
         vm.resetStates()
         vm.mutex.Unlock()
-        vms.rwlock.Lock()
-        vms.usedPorts[vm.Run.Port] = false
-        vms.usedRAM -= estimatedVmRAM
-        vms.rwlock.Unlock()
     }
 
     if err = vm.start(port, pwd, endofExecFn); err != nil {
+        vms.usedPorts[port] = false
         return err
     }
     return nil
 }
 
-// Starts a VM by its ID using randomly generated port number and password.
-// Returns the port on which the VM is running and the access password.
-func (vms *VMs)StartVM(vmID uuid.UUID) (int, string, error) {
+// Allocates and returns a free port randomly chosen between VMSpiceMinPort and
+// VMSpiceMaxPort (inclusive).
+// Beware: this function updates the vms map.
+func (vms *VMs)allocateFreeRandomPort() int {
+    vms.rwlock.Lock()
+    defer vms.rwlock.Unlock()
 
-    // Locates a free port randomly chosen between VMSpiceMinPort and VMSpiceMaxPort (inclusive).
-    var port int
     for {
-        port = utils.Rand(c.VMSpiceMinPort, c.VMSpiceMaxPort)
+        port := utils.Rand(c.VMSpiceMinPort, c.VMSpiceMaxPort)
         if !vms.usedPorts[port] {
             if utils.IsPortAvailable(port) {
                 vms.usedPorts[port] = true
-                break
+                return port
             }
         }
     }
+}
+
+// Starts a VM by its ID using randomly generated port number and password.
+// Returns the port on which the VM is running and the access password.
+func (vms *VMs)StartVM(vmID uuid.UUID) (int, string, error) {
+    port := vms.allocateFreeRandomPort()
 
     // Randomly generates a 8 characters long password with 4 digits, 0 symbols,
     // allowing upper and lower case letters, disallowing repeat characters.
@@ -254,7 +273,7 @@ func (vms *VMs)StartVM(vmID uuid.UUID) (int, string, error) {
         return -1, "", errors.New("Failed starting VM: password generation error: "+err.Error())
     }
 
-    if err = vms.StartVMWithCreds(vmID, port, pwd); err != nil {
+    if err = vms.StartVMWithCreds(vmID, port, false, pwd); err != nil {
         return -1, "", err
     }
     return port, pwd, nil