X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=DESIGN;h=f3e9309d8cb9c6ea5b6581e2b6f006538b0d019a;hb=refs%2Fheads%2Fof1.1;hp=e59dc6eba94953d7ee07ade4167c648680130014;hpb=f66b87de59564e70bf6325e6bd211e45243187c8;p=openvswitch diff --git a/DESIGN b/DESIGN index e59dc6eb..f3e9309d 100644 --- a/DESIGN +++ b/DESIGN @@ -17,8 +17,14 @@ given controller receives OpenFlow asynchronous messages. This section describes how all of these features interact. First, a service controller never receives any asynchronous messages -unless it explicitly configures a miss_send_len greater than zero with -an OFPT_SET_CONFIG message. +unless it changes its miss_send_len from the service controller +default of zero in one of the following ways: + + - Sending an OFPT_SET_CONFIG message with nonzero miss_send_len. + + - Sending any NXT_SET_ASYNC_CONFIG message: as a side effect, this + message changes the miss_send_len to + OFP_DEFAULT_MISS_SEND_LEN (128) for service controllers. Second, OFPT_FLOW_REMOVED and NXT_FLOW_REMOVED messages are generated only if the flow that was removed had the OFPFF_SEND_FLOW_REM flag @@ -146,6 +152,121 @@ sends flow_removed message --- --- --- % % receive the generated messages.) +VLAN Matching +============= + +The 802.1Q VLAN header causes more trouble than any other 4 bytes in +networking. More specifically, three versions of OpenFlow and Open +vSwitch have among them four different ways to match the contents and +presence of the VLAN header. The following table describes how each +version works. + + Match NXM OF1.0 OF1.1 OF1.2 + ----- --------- ----------- ----------- ------------ + [1] 0000/0000 ????/1,??/? ????/1,??/? 0000/0000,-- + [2] 0000/ffff ffff/0,??/? ffff/0,??/? 0000/ffff,-- + [3] 1xxx/1fff 0xxx/0,??/1 0xxx/0,??/1 1xxx/ffff,-- + [4] z000/f000 ????/1,0y/0 fffe/0,0y/0 1000/1000,0y + [5] zxxx/ffff 0xxx/0,0y/0 0xxx/0,0y/0 1xxx/ffff,0y + [6] 0000/0fff + [7] 0000/f000 + [8] 0000/efff + [9] 1001/1001 1001/1001,-- + [10] 3000/3000 + +Each column is interpreted as follows. + + - Match: See the list below. + + - NXM: xxxx/yyyy means NXM_OF_VLAN_TCI_W with value xxxx and mask + yyyy. A mask of 0000 is equivalent to omitting + NXM_OF_VLAN_TCI(_W), a mask of ffff is equivalent to + NXM_OF_VLAN_TCI. + + - OF1.0 and OF1.1: wwww/x,yy/z means dl_vlan wwww, OFPFW_DL_VLAN + x, dl_vlan_pcp yy, and OFPFW_DL_VLAN_PCP z. ? means that the + given nibble is ignored (and conventionally 0 for wwww or z, + conventionally 1 for x or z). means that the given match + is not supported. + + - OF1.2: xxxx/yyyy,zz means OXM_OF_VLAN_VID_W with value xxxx and + mask yyyy, and OXM_OF_VLAN_PCP (which is not maskable) with + value zz. A mask of 0000 is equivalent to omitting + OXM_OF_VLAN_VID(_W), a mask of ffff is equivalent to + OXM_OF_VLAN_VID. -- means that OXM_OF_VLAN_PCP is omitted. + means that the given match is not supported. + +The matches are: + + [1] Matches any packet, that is, one without an 802.1Q header or with + an 802.1Q header with any TCI value. + + [2] Matches only packets without an 802.1Q header. + + NXM: Any match with (vlan_tci == 0) and (vlan_tci_mask & 0x1000) + != 0 is equivalent to the one listed in the table. + + OF1.0: The spec doesn't define behavior if dl_vlan is set to + 0xffff and OFPFW_DL_VLAN_PCP is not set. + + OF1.1: The spec says explicitly to ignore dl_vlan_pcp when + dl_vlan is set to 0xffff. + + OF1.2: The spec doesn't say what should happen if (vlan_vid == 0) + and (vlan_vid_mask & 0x1000) != 0 but (vlan_vid_mask != 0x1000), + but it would be straightforward to also interpret as [2]. + + [3] Matches only packets that have an 802.1Q header with VID xxx (and + any PCP). + + [4] Matches only packets that have an 802.1Q header with PCP y (and + any VID). + + NXM: z is ((y << 1) | 1). + + OF1.0: The spec isn't very clear, but OVS implements it this way. + + OF1.2: Presumably other masks such that (vlan_vid_mask & 0x1fff) + == 0x1000 would also work, but the spec doesn't define their + behavior. + + [5] Matches only packets that have an 802.1Q header with VID xxx and + PCP y. + + NXM: z is ((y << 1) | 1). + + OF1.2: Presumably other masks such that (vlan_vid_mask & 0x1fff) + == 0x1fff would also work. + + [6] Matches packets with no 802.1Q header or with an 802.1Q header + with a VID of 0. Only possible with NXM. + + [7] Matches packets with no 802.1Q header or with an 802.1Q header + with a PCP of 0. Only possible with NXM. + + [8] Matches packets with no 802.1Q header or with an 802.1Q header + with both VID and PCP of 0. Only possible with NXM. + + [9] Matches only packets that have an 802.1Q header with an + odd-numbered VID (and any PCP). Only possible with NXM and + OF1.2. (This is just an example; one can match on any desired + VID bit pattern.) + +[10] Matches only packets that have an 802.1Q header with an + odd-numbered PCP (and any VID). Only possible with NXM. (This + is just an example; one can match on any desired VID bit + pattern.) + +Additional notes: + + - OF1.2: The top three bits of OXM_OF_VLAN_VID are fixed to zero, + so bits 13, 14, and 15 in the masks listed in the table may be + set to arbitrary values, as long as the corresponding value bits + are also zero. The suggested ffff mask for [2], [3], and [5] + allows a shorter OXM representation (the mask is omitted) than + the minimal 1fff mask. + + Flow Cookies ============ @@ -198,11 +319,16 @@ behavior with the following extensions: arbitrary masks. This is much like the equivalent OpenFlow 1.1 feature. - - However, unlike OpenFlow 1.1, OFPC_MODIFY and - OFPFC_MODIFY_STRICT, regardless of whether there was a match - based on a cookie or not, always add a new flow if there is - no match, and they always update the cookies of flows that - they do match. + - Like OpenFlow 1.1, OFPC_MODIFY and OFPFC_MODIFY_STRICT add a + new flow if there is no match and the mask is zero (or not + given). + + - The "cookie" field in OFPT_FLOW_MOD and NXT_FLOW_MOD messages + is used as the cookie value for OFPFC_ADD commands, as + described in OpenFlow 1.0. For OFPFC_MODIFY and + OFPFC_MODIFY_STRICT commands, the "cookie" field is used as a + new cookie for flows that match unless it is UINT64_MAX, in + which case the flow's cookie is not updated. - NXT_PACKET_IN (the Nicira extended version of OFPT_PACKET_IN) reports the cookie of the rule that @@ -210,6 +336,21 @@ behavior with the following extensions: packet. (Older versions of OVS used all-0-bits instead of all-1-bits.) +The following table shows the handling of different protocols when +receiving OFPFC_MODIFY and OFPFC_MODIFY_STRICT messages. A mask of 0 +indicates either an explicit mask of zero or an implicit one by not +specifying the NXM_NX_COOKIE(_W) field. + + Match Update Add on miss Add on miss + cookie cookie mask!=0 mask==0 + ====== ====== =========== =========== +OpenFlow 1.0 no yes +OpenFlow 1.1 yes no no yes +OpenFlow 1.2 yes no no no +NXM yes yes* no yes + +* Updates the flow's cookie unless the "cookie" field is UINT64_MAX. + Multiple Table Support ====================== @@ -586,6 +727,39 @@ The following are explicitly *not* supported by in-band control: gateway. +Action Reproduction +=================== + +It seems likely that many controllers, at least at startup, use the +OpenFlow "flow statistics" request to obtain existing flows, then +compare the flows' actions against the actions that they expect to +find. Before version 1.8.0, Open vSwitch always returned exact, +byte-for-byte copies of the actions that had been added to the flow +table. The current version of Open vSwitch does not always do this in +some exceptional cases. This section lists the exceptions that +controller authors must keep in mind if they compare actual actions +against desired actions in a bytewise fashion: + + - Open vSwitch zeros padding bytes in action structures, + regardless of their values when the flows were added. + + - Open vSwitch "normalizes" the instructions in OpenFlow 1.1 + (and later) in the following way: + + * OVS sorts the instructions into the following order: + Apply-Actions, Clear-Actions, Write-Actions, + Write-Metadata, Goto-Table. + + * OVS drops Apply-Actions instructions that have empty + action lists. + + * OVS drops Write-Actions instructions that have empty + action sets. + +Please report other discrepancies, if you notice any, so that we can +fix or document them. + + Suggestions ===========