[libvirt] [PATCH] Add virNetlinkNewLink for simplifying virNetDev*Create
Shi Lei
shi_lei at massclouds.com
Thu Aug 30 06:27:05 UTC 2018
Thanks for your comments.
But I have several questions, please see below...
On 2018-08-29 at 19:43, Erik Skultety wrote:
>On Thu, Aug 23, 2018 at 12:15:08PM +0800, Shi Lei wrote:
>> This patch adds virNetlinkNewLink for simplifying virNetDevMacVLanCreate
>> and virNetDevBridgeCreate.
>>
>> Signed-off-by: Shi Lei <shi_lei at massclouds.com>
>> ---
>
>There are multiple changes happening in this patch so it will need to be split
>into several patches, see below...
Okay. Then the v2 series should be like:
[patch v2 0/4]: ... cover ...
[patch v2 1/4]: Add wrapper macros to make code more readable
[patch v2 2/4]: Introduce virNetlinkNewLink
[patch v2 3/4]: Replace the implementation of virNetDevBridgeCreate
[patch v2 4/4]: Replace the implementation of virNetDevMacVLanCreate
>
>> src/libvirt_private.syms | 1 +
>> src/util/virnetdevbridge.c | 73 +++--------------------
>> src/util/virnetdevmacvlan.c | 137 ++++++++++++++------------------------------
>> src/util/virnetlink.c | 104 +++++++++++++++++++++++++++++++++
>> src/util/virnetlink.h | 8 +++
>> 5 files changed, 164 insertions(+), 159 deletions(-)
>>
>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>> index 47ea35f..23931ba 100644
>> --- a/src/libvirt_private.syms
>> +++ b/src/libvirt_private.syms
>> @@ -2439,6 +2439,7 @@ virNetlinkEventServiceStop;
>> virNetlinkEventServiceStopAll;
>> virNetlinkGetErrorCode;
>> virNetlinkGetNeighbor;
>> +virNetlinkNewLink;
>> virNetlinkShutdown;
>> virNetlinkStartup;
>>
>> diff --git a/src/util/virnetdevbridge.c b/src/util/virnetdevbridge.c
>> index bc377b5..1f5b37e 100644
>> --- a/src/util/virnetdevbridge.c
>> +++ b/src/util/virnetdevbridge.c
>> @@ -417,77 +417,22 @@ virNetDevBridgeCreate(const char *brname)
>> {
>> /* use a netlink RTM_NEWLINK message to create the bridge */
>> const char *type = "bridge";
>> - struct nlmsgerr *err;
>> - struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
>> - unsigned int recvbuflen;
>> - struct nlattr *linkinfo;
>> - VIR_AUTOPTR(virNetlinkMsg) nl_msg = NULL;
>> - VIR_AUTOFREE(struct nlmsghdr *) resp = NULL;
>> + int error = 0;
>>
>> - nl_msg = nlmsg_alloc_simple(RTM_NEWLINK,
>> - NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL);
>> - if (!nl_msg) {
>> - virReportOOMError();
>> - return -1;
>> - }
>> -
>> - if (nlmsg_append(nl_msg, &ifinfo, sizeof(ifinfo), NLMSG_ALIGNTO) < 0)
>> - goto buffer_too_small;
>> - if (nla_put(nl_msg, IFLA_IFNAME, strlen(brname)+1, brname) < 0)
>> - goto buffer_too_small;
>> - if (!(linkinfo = nla_nest_start(nl_msg, IFLA_LINKINFO)))
>> - goto buffer_too_small;
>> - if (nla_put(nl_msg, IFLA_INFO_KIND, strlen(type), type) < 0)
>> - goto buffer_too_small;
>> - nla_nest_end(nl_msg, linkinfo);
>> -
>> - if (virNetlinkCommand(nl_msg, &resp, &recvbuflen, 0, 0,
>> - NETLINK_ROUTE, 0) < 0) {
>> - return -1;
>> - }
>> -
>> - if (recvbuflen < NLMSG_LENGTH(0) || resp == NULL)
>> - goto malformed_resp;
>> -
>> - switch (resp->nlmsg_type) {
>> - case NLMSG_ERROR:
>> - err = (struct nlmsgerr *)NLMSG_DATA(resp);
>> - if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
>> - goto malformed_resp;
>> -
>> - if (err->error < 0) {
>> + if (virNetlinkNewLink(NULL, brname, NULL, type, NULL, NULL, &error) < 0) {
>> # if defined(HAVE_STRUCT_IFREQ) && defined(SIOCBRADDBR)
>> - if (err->error == -EOPNOTSUPP) {
>> - /* fallback to ioctl if netlink doesn't support creating
>> - * bridges
>> - */
>> - return virNetDevBridgeCreateWithIoctl(brname);
>> - }
>> -# endif
>> -
>> - virReportSystemError(-err->error,
>> - _("error creating bridge interface %s"),
>> - brname);
>> - return -1;
>> + if (error == -EOPNOTSUPP) {
>> + /* fallback to ioctl if netlink doesn't support creating bridges */
>> + return virNetDevBridgeCreateWithIoctl(brname);
>> }
>> - break;
>> +# endif
>> + virReportSystemError(-error, _("error creating bridge interface %s"),
>> + brname);
>>
>> - case NLMSG_DONE:
>> - break;
>> - default:
>> - goto malformed_resp;
>> + return -1;
>> }
>>
>> return 0;
>> -
>> - malformed_resp:
>> - virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> - _("malformed netlink response message"));
>> - return -1;
>> - buffer_too_small:
>> - virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> - _("allocated netlink buffer is too small"));
>> - return -1;
>> }
>>
>>
>> diff --git a/src/util/virnetdevmacvlan.c b/src/util/virnetdevmacvlan.c
>> index 2035b1f..1629add 100644
>> --- a/src/util/virnetdevmacvlan.c
>> +++ b/src/util/virnetdevmacvlan.c
>> @@ -283,6 +283,37 @@ virNetDevMacVLanReleaseName(const char *name)
>> }
>>
>>
>> +static int
>> +virNetDevMacVLanCreateCallback(struct nl_msg *nl_msg, const void *opaque)
>> +{
>> + const uint32_t *mode = (const uint32_t *) opaque;
>> + if (!nl_msg || !opaque) {
>> + virReportError(VIR_ERR_INTERNAL_ERROR,
>> + _("nl_msg %p or opaque %p is NULL"),
>> + nl_msg, opaque);
>> + return -1;
>> + }
>> +
>> + if (*mode > 0) {
>> + struct nlattr *info_data;
>> + if (!(info_data = nla_nest_start(nl_msg, IFLA_INFO_DATA)))
>> + goto buffer_too_small;
>> +
>> + if (nla_put(nl_msg, IFLA_MACVLAN_MODE, sizeof(*mode), mode) < 0)
>> + goto buffer_too_small;
>> +
>> + nla_nest_end(nl_msg, info_data);
>> + }
>> +
>> + return 0;
>> +
>> + buffer_too_small:
>> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> + _("allocated netlink buffer is too small"));
>> + return -1;
>> +}
>
>Having a callback just to add a nested data into nl_msg doesn't feel like the
>right approach, I'd expect a callback to do more specific stuff, this should be
>special-cased in virNetlinkNewLink.
I looked through the code for ip-link in iproute2 which could be a good example
for netlink. And I found that the differences of attributes of various net-devices are
confined to IFLA_INFO_DATA or IFLA_INFO_SLAVE_DATA(this is not used in libvirt).
The code fragment in iplink.c:
if (ulinep && !strcmp(ulinep, "_slave")) {
... ...
lu = get_link_slave_kind(slavebuf);
iflatype = IFLA_INFO_SLAVE_DATA;
} else {
=> lu = get_link_kind(type); /* Get pointer to the driver for this type */
=> iflatype = IFLA_INFO_DATA; /* NEST will be for IFLA_INFO_DATA */
}
if (lu && argc) {
=> struct rtattr *data = addattr_nest(&req.n, sizeof(req), iflatype); /* NEST BEGIN */
****************************
if (lu->parse_opt &&
lu->parse_opt(lu, argc, argv, &req.n))
return -1;
****************************
^The lu points to various types of net-drivers(e.g. macvlan/bridge/vxlan/vlan ...)
which pack all special self-attributes in their parse_opt callback
=> addattr_nest_end(&req.n, data); /* NEST END */
So I think that it's reasonable for us to have a callback to handle it just as iproute2
since iproute2 could almost create all the types of net-devices.
>
>> +
>> +
>> /**
>> * virNetDevMacVLanCreate:
>> *
>> @@ -307,113 +338,29 @@ virNetDevMacVLanCreate(const char *ifname,
>> uint32_t macvlan_mode,
>> int *retry)
>> {
>
>^This replacement would be the last patch in the series.
Okay.
>
>> - int rc = -1;
>> - struct nlmsgerr *err;
>> - struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
>> int ifindex;
>> - unsigned int recvbuflen;
>> - struct nl_msg *nl_msg;
>> - struct nlattr *linkinfo, *info_data;
>> - char macstr[VIR_MAC_STRING_BUFLEN];
>> - VIR_AUTOFREE(struct nlmsghdr *) resp = NULL;
>> -
>> - if (virNetDevGetIndex(srcdev, &ifindex) < 0)
>> - return -1;
>> -
>> + int error = 0;
>> *retry = 0;
>>
>> - nl_msg = nlmsg_alloc_simple(RTM_NEWLINK,
>> - NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL);
>> - if (!nl_msg) {
>> - virReportOOMError();
>> + if (virNetDevGetIndex(srcdev, &ifindex) < 0)
>> return -1;
>> - }
>> -
>> - if (nlmsg_append(nl_msg, &ifinfo, sizeof(ifinfo), NLMSG_ALIGNTO) < 0)
>> - goto buffer_too_small;
>> -
>> - if (nla_put_u32(nl_msg, IFLA_LINK, ifindex) < 0)
>> - goto buffer_too_small;
>> -
>> - if (nla_put(nl_msg, IFLA_ADDRESS, VIR_MAC_BUFLEN, macaddress) < 0)
>> - goto buffer_too_small;
>> -
>> - if (ifname &&
>> - nla_put(nl_msg, IFLA_IFNAME, strlen(ifname)+1, ifname) < 0)
>> - goto buffer_too_small;
>>
>> - if (!(linkinfo = nla_nest_start(nl_msg, IFLA_LINKINFO)))
>> - goto buffer_too_small;
>> -
>> - if (nla_put(nl_msg, IFLA_INFO_KIND, strlen(type), type) < 0)
>> - goto buffer_too_small;
>> -
>> - if (macvlan_mode > 0) {
>> - if (!(info_data = nla_nest_start(nl_msg, IFLA_INFO_DATA)))
>> - goto buffer_too_small;
>> -
>> - if (nla_put(nl_msg, IFLA_MACVLAN_MODE, sizeof(macvlan_mode),
>> - &macvlan_mode) < 0)
>> - goto buffer_too_small;
>> -
>> - nla_nest_end(nl_msg, info_data);
>> - }
>> -
>> - nla_nest_end(nl_msg, linkinfo);
>> -
>> - if (virNetlinkCommand(nl_msg, &resp, &recvbuflen, 0, 0,
>> - NETLINK_ROUTE, 0) < 0) {
>> - goto cleanup;
>> - }
>> -
>> - if (recvbuflen < NLMSG_LENGTH(0) || resp == NULL)
>> - goto malformed_resp;
>> -
>> - switch (resp->nlmsg_type) {
>> - case NLMSG_ERROR:
>> - err = (struct nlmsgerr *)NLMSG_DATA(resp);
>> - if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
>> - goto malformed_resp;
>> -
>> - switch (err->error) {
>> -
>> - case 0:
>> - break;
>> -
>> - case -EEXIST:
>> + if (virNetlinkNewLink(&ifindex, ifname, macaddress, type,
>> + virNetDevMacVLanCreateCallback, &macvlan_mode,
>> + &error) < 0) {
>> + char macstr[VIR_MAC_STRING_BUFLEN];
>> + if (error == -EEXIST)
>> *retry = 1;
>> - goto cleanup;
>> -
>> - default:
>> - virReportSystemError(-err->error,
>> + else
>> + virReportSystemError(-error,
>> _("error creating %s interface %s@%s (%s)"),
>> type, ifname, srcdev,
>> virMacAddrFormat(macaddress, macstr));
>> - goto cleanup;
>> - }
>> - break;
>> -
>> - case NLMSG_DONE:
>> - break;
>>
>> - default:
>> - goto malformed_resp;
>> + return -1;
>> }
>>
>> - rc = 0;
>> - cleanup:
>> - nlmsg_free(nl_msg);
>> - return rc;
>> -
>> - malformed_resp:
>> - virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> - _("malformed netlink response message"));
>> - goto cleanup;
>> -
>> - buffer_too_small:
>> - virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> - _("allocated netlink buffer is too small"));
>> - goto cleanup;
>> + return 0;
>> }
>>
>> /**
>> diff --git a/src/util/virnetlink.c b/src/util/virnetlink.c
>> index 8f06446..817e347 100644
>> --- a/src/util/virnetlink.c
>> +++ b/src/util/virnetlink.c
>> @@ -489,6 +489,110 @@ virNetlinkDumpLink(const char *ifname, int ifindex,
>>
>>
>> /**
>> + * virNetlinkNewLink:
>
>Introduction of this function should come in a separate patch before you start
>replacing the existing ones.
Okay.
>
>> + *
>> + * @ifindex: The index for the 'link' device
>> + * @ifname: The name of the link
>> + * @mac: The MAC address of the device
>
>Most of ^these attributes could be packed into a virNetlinkNewLinkData
>structure (or something similarly named). You'll have to test check for
>VIR_DOMAIN_NET_TYPE_DIRECT and VIR_NETDEV_MACVLAN_MODE_VEPA according to my
>comments below inside <comment_block>...
I have studied your comments inside <comment_block>, but I still don't know how to
test check for VIR_DOMAIN_NET_TYPE_DIRECT and VIR_NETDEV_MACVLAN_MODE_VEPA.
Could you explain it for me? :-)
>
>> + * @type: The type of device, i.e., "bridge", "macvtap", "macvlan"
>> + * @cb: The callback for filling in IFLA_INFO_DATA for this type
>
>I don't think callback will be necessary
I think that it's reasonable to use callback here.
Another mode might be:
1) pre-alloc buffer and fill in IFLA_INFO_DATA
2) pass the buffer pointer as a param into virNetlinkNewLink which will
embed it into nlmsg
3) free the buffer
I think that this mode might be a bit more complicated and it's hard to find good references.
>
>> + * @opaque: opaque for the callback
>> + * @error: for retrieving error code
>
>^see below for my comment on return value...
Okay.
>
>> + *
>> + * Create a network "link" (aka interface aka device) with the given
>> + * args. This works for many different types of network devices,
>> + * including macvtap and bridges.
>> + *
>> + * Returns 0 on success, -1 on fatal error.
>
>Since this is a nice libvirt wrapper around the netlink communication
>machinery, I think that returning -<netlink_error> in case of an error is
>reasonable. Then, each of the callers of this API can handle the return values
>as they please.
Okay. I will use netlink error as return-value.
But how to handle -1?
1) always return -1 for *other* failures
2) return -ENOMEM for OutofMemory; return -ENOBUFS for buffer_too_small; ...
I should take which one?
>
>> + */
>> +int
>> +virNetlinkNewLink(const int *ifindex,
>> + const char *ifname,
>> + const virMacAddr *mac,
>> + const char *type,
>> + virNetlinkNewLinkCallback cb,
>> + const void *opaque,
>> + int *error)
>> +{
>> + struct nlmsgerr *err;
>> + struct nlattr *linkinfo;
>> + unsigned int buflen;
>> + struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
>> + VIR_AUTOPTR(virNetlinkMsg) nl_msg = NULL;
>> + VIR_AUTOFREE(struct nlmsghdr *) resp = NULL;
>> +
>> + *error = 0;
>> +
>> + nl_msg = nlmsg_alloc_simple(RTM_NEWLINK,
>> + NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL);
>> + if (!nl_msg) {
>> + virReportOOMError();
>> + return -1;
>> + }
>> +
>> + if (nlmsg_append(nl_msg, &ifinfo, sizeof(ifinfo), NLMSG_ALIGNTO) < 0)
>> + goto buffer_too_small;
>> +
>
No offence. Let me try talking about nla_put* in comment_block.
><comment_block>
>
>> + if (ifindex && nla_put_u32(nl_msg, IFLA_LINK, *ifindex) < 0)
>
>pre-existing, but is there a particular reason why ^this has to be u32??
prototype of nla_put_u32:
int nla_put_u32(struct nl_msg *msg, int attrtype, uint32_t value);
It is used for adding 32 bit integer into msg.
We got ifindex by calling ioctl with SIOCGIFINDEX and this ifindex >= 0.
So I think that it's right to use nla_put_u32.
>
>> + goto buffer_too_small;
>> +
>> + if (mac && nla_put(nl_msg, IFLA_ADDRESS, VIR_MAC_BUFLEN, mac) < 0)
>> + goto buffer_too_small;
>
>Similarly, is there a reason why ^this is not necessary to be u32?
prototype of nla_put:
int nla_put(struct nl_msg *msg, int attrtype, int datalen, const void *data);
It means put a sequence of octets into msg. It could be used for string and
other packed struct.
The type of mac is struct virMacAddr which size is VIR_MAC_BUFLEN.
So I think it's right.
>
>> +
>> + if (ifname && nla_put(nl_msg, IFLA_IFNAME, strlen(ifname)+1, ifname) < 0)
>> + goto buffer_too_small;
>> +
>> + if (!(linkinfo = nla_nest_start(nl_msg, IFLA_LINKINFO)))
>
>Since we're already touching the code, I would find it more readable if ^this
>was written as linkinfo = nla_nest_start. The reason for that is that it's not
>immediately visible where the matching counterpart to "nla_nest_end" is.
Okay.
>
>> + goto buffer_too_small;
>> +
>> + if (nla_put(nl_msg, IFLA_INFO_KIND, strlen(type), type) < 0)
>
>I'm puzzled why ^this doesn't need strlen(foo)+1 instead of plain strlen(foo)
This code is same as iproute2. There's no problem here.
In net/core/rtnetlink.c of kernel (source v4.4.0):
nla_strlcpy(kind, linkinfo[IFLA_INFO_KIND], sizeof(kind));
and the implementation of nla_strlcpy:
size_t nla_strlcpy(char *dst, const struct nlattr *nla, size_t dstsize)
{
size_t srclen = nla_len(nla); /* whatever it is strlen(foo)+1 or strlen(foo) */
char *src = nla_data(nla);
=> if (srclen > 0 && src[srclen - 1] == '\0')
=> srclen--;
But I think it should always be strlen(foo)+1 for consistency of code.
>
>> + goto buffer_too_small;
>
></comment_block>
>
>We could actually create a wrapper macro around nla_put which would make the
>block (begin-end) tiny more readable. See my notes above, as I have further
>questions...Now, the macros would again be a separate patch to make the change
>more gradual. Depending on the comments to my questions above, the macro would
>either take the size of the type and always call nla_put or a specialized
>nla_put_<string|u32|whatever> function. I'm CC'ing Laine to help answering my
>questions inside <comment_block>.
>
>Erik
I think that the usage of nla_put* is clear now.
So I don't know how to create wrapper macros.
Could you give me some instructions for it?
Regards,
Shi Lei
>
>> +
>> + if (cb && cb(nl_msg, opaque) < 0)
>> + return -1;
>
>> +
>> + nla_nest_end(nl_msg, linkinfo);
>> +
>> + if (virNetlinkCommand(nl_msg, &resp, &buflen, 0, 0, NETLINK_ROUTE, 0) < 0)
>> + return -1;
>> +
>> + if (buflen < NLMSG_LENGTH(0) || resp == NULL)
>> + goto malformed_resp;
>> +
>> + switch (resp->nlmsg_type) {
>> + case NLMSG_ERROR:
>> + err = (struct nlmsgerr *)NLMSG_DATA(resp);
>> + if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
>> + goto malformed_resp;
>> +
>> + if (err->error < 0) {
>> + *error = err->error;
>> + return -1;
>> + }
>> + break;
>> +
>> + case NLMSG_DONE:
>> + break;
>> +
>> + default:
>> + goto malformed_resp;
>> + }
>> +
>> + return 0;
>> +
>> + malformed_resp:
>> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> + _("malformed netlink response message"));
>> + return -1;
>> +
>> + buffer_too_small:
>> + virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>> + _("allocated netlink buffer is too small"));
>> + return -1;
>> +}
>> +
>> +
>> +/**
>> * virNetlinkDelLink:
>> *
>> * @ifname: Name of the link
>> diff --git a/src/util/virnetlink.h b/src/util/virnetlink.h
>> index 1e1e616..195c7bb 100644
>> --- a/src/util/virnetlink.h
>> +++ b/src/util/virnetlink.h
>> @@ -65,6 +65,14 @@ int virNetlinkDumpCommand(struct nl_msg *nl_msg,
>> unsigned int protocol, unsigned int groups,
>> void *opaque);
>>
>> +typedef int (*virNetlinkNewLinkCallback)(struct nl_msg *nl_msg,
>> + const void *opaque);
>> +
>> +int virNetlinkNewLink(const int *ifindex, const char *ifname,
>> + const virMacAddr *macaddress, const char *type,
>> + virNetlinkNewLinkCallback cb, const void *opaque,
>> + int *error);
>> +
>> typedef int (*virNetlinkDelLinkFallback)(const char *ifname);
>>
>> int virNetlinkDelLink(const char *ifname, virNetlinkDelLinkFallback fallback);
>> --
>> 2.7.4
>>
>>
>> --
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