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flow, tcp: Generalise TCP hash table to general flow hash table
Move the data structures and helper functions for the TCP hash table to flow.c, making it a general hash table indexing sides of flows. This is largely code motion and straightforward renames. There are two semantic changes: * flow_lookup_af() now needs to verify that the entry has a matching protocol and interface as well as matching addresses and ports. * We double the size of the hash table, because it's now at least theoretically possible for both sides of each flow to be hashed. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson
Stefano Brivio
parent
163a339214
commit
acca4235c4
5 changed files with 172 additions and 145 deletions
155
flow.c
155
flow.c
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@ -105,6 +105,16 @@ unsigned flow_first_free;
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union flow flowtab[FLOW_MAX];
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static const union flow *flow_new_entry; /* = NULL */
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/* Hash table to index it */
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#define FLOW_HASH_LOAD 70 /* % */
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#define FLOW_HASH_SIZE ((2 * FLOW_MAX * 100 / FLOW_HASH_LOAD))
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/* Table for lookup from flowside information */
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static flow_sidx_t flow_hashtab[FLOW_HASH_SIZE];
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static_assert(ARRAY_SIZE(flow_hashtab) >= 2 * FLOW_MAX,
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"Safe linear probing requires hash table with more entries than the number of sides in the flow table");
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/* Last time the flow timers ran */
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static struct timespec flow_timer_run;
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@ -116,9 +126,9 @@ static struct timespec flow_timer_run;
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* @faddr: Forwarding address (pointer to in_addr or in6_addr)
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* @fport: Forwarding port
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*/
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void flowside_from_af(struct flowside *side, sa_family_t af,
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const void *eaddr, in_port_t eport,
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const void *faddr, in_port_t fport)
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static void flowside_from_af(struct flowside *side, sa_family_t af,
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const void *eaddr, in_port_t eport,
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const void *faddr, in_port_t fport)
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{
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if (faddr)
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inany_from_af(&side->faddr, af, faddr);
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@ -410,8 +420,8 @@ void flow_alloc_cancel(union flow *flow)
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*
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* Return: hash value
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*/
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uint64_t flow_hash(const struct ctx *c, uint8_t proto, uint8_t pif,
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const struct flowside *side)
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static uint64_t flow_hash(const struct ctx *c, uint8_t proto, uint8_t pif,
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const struct flowside *side)
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{
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struct siphash_state state = SIPHASH_INIT(c->hash_secret);
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@ -430,6 +440,136 @@ uint64_t flow_hash(const struct ctx *c, uint8_t proto, uint8_t pif,
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(uint64_t)side->eport);
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}
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/**
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* flow_sidx_hash() - Calculate hash value for given side of a given flow
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* @c: Execution context
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* @sidx: Flow & side index to get hash for
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*
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* Return: hash value, of the flow & side represented by @sidx
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*/
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static uint64_t flow_sidx_hash(const struct ctx *c, flow_sidx_t sidx)
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{
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const struct flow_common *f = &flow_at_sidx(sidx)->f;
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return flow_hash(c, FLOW_PROTO(f),
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f->pif[sidx.sidei], &f->side[sidx.sidei]);
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}
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/**
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* flow_hash_probe() - Find hash bucket for a flow
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* @c: Execution context
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* @sidx: Flow and side to find bucket for
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*
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* Return: If @sidx is in the hash table, its current bucket, otherwise a
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* suitable free bucket for it.
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*/
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static inline unsigned flow_hash_probe(const struct ctx *c, flow_sidx_t sidx)
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{
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unsigned b = flow_sidx_hash(c, sidx) % FLOW_HASH_SIZE;
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/* Linear probing */
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while (flow_sidx_valid(flow_hashtab[b]) &&
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!flow_sidx_eq(flow_hashtab[b], sidx))
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b = mod_sub(b, 1, FLOW_HASH_SIZE);
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return b;
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}
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/**
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* flow_hash_insert() - Insert side of a flow into into hash table
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* @c: Execution context
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* @sidx: Flow & side index
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*/
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void flow_hash_insert(const struct ctx *c, flow_sidx_t sidx)
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{
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unsigned b = flow_hash_probe(c, sidx);
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flow_hashtab[b] = sidx;
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flow_dbg(flow_at_sidx(sidx), "Side %u hash table insert: bucket: %u",
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sidx.sidei, b);
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}
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/**
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* flow_hash_remove() - Drop side of a flow from the hash table
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* @c: Execution context
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* @sidx: Side of flow to remove
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*/
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void flow_hash_remove(const struct ctx *c, flow_sidx_t sidx)
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{
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unsigned b = flow_hash_probe(c, sidx), s;
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if (!flow_sidx_valid(flow_hashtab[b]))
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return; /* Redundant remove */
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flow_dbg(flow_at_sidx(sidx), "Side %u hash table remove: bucket: %u",
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sidx.sidei, b);
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/* Scan the remainder of the cluster */
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for (s = mod_sub(b, 1, FLOW_HASH_SIZE);
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flow_sidx_valid(flow_hashtab[s]);
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s = mod_sub(s, 1, FLOW_HASH_SIZE)) {
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unsigned h = flow_sidx_hash(c, flow_hashtab[s]) % FLOW_HASH_SIZE;
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if (!mod_between(h, s, b, FLOW_HASH_SIZE)) {
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/* flow_hashtab[s] can live in flow_hashtab[b]'s slot */
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debug("hash table remove: shuffle %u -> %u", s, b);
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flow_hashtab[b] = flow_hashtab[s];
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b = s;
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}
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}
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flow_hashtab[b] = FLOW_SIDX_NONE;
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}
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/**
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* flowside_lookup() - Look for a matching flowside in the flow table
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* @c: Execution context
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* @proto: Protocol of the flow (IP L4 protocol number)
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* @pif: pif to look for in the table
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* @side: Flowside to look for in the table
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*
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* Return: sidx of the matching flow & side, FLOW_SIDX_NONE if not found
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*/
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static flow_sidx_t flowside_lookup(const struct ctx *c, uint8_t proto,
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uint8_t pif, const struct flowside *side)
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{
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flow_sidx_t sidx;
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union flow *flow;
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unsigned b;
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b = flow_hash(c, proto, pif, side) % FLOW_HASH_SIZE;
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while ((sidx = flow_hashtab[b], flow = flow_at_sidx(sidx)) &&
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!(FLOW_PROTO(&flow->f) == proto &&
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flow->f.pif[sidx.sidei] == pif &&
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flowside_eq(&flow->f.side[sidx.sidei], side)))
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b = (b + 1) % FLOW_HASH_SIZE;
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return flow_hashtab[b];
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}
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/**
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* flow_lookup_af() - Look up a flow given addressing information
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* @c: Execution context
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* @proto: Protocol of the flow (IP L4 protocol number)
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* @pif: Interface of the flow
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* @af: Address family, AF_INET or AF_INET6
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* @eaddr: Guest side endpoint address (guest local address)
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* @faddr: Guest side forwarding address (guest remote address)
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* @eport: Guest side endpoint port (guest local port)
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* @fport: Guest side forwarding port (guest remote port)
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*
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* Return: sidx of the matching flow & side, FLOW_SIDX_NONE if not found
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*/
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flow_sidx_t flow_lookup_af(const struct ctx *c,
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uint8_t proto, uint8_t pif, sa_family_t af,
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const void *eaddr, const void *faddr,
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in_port_t eport, in_port_t fport)
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{
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struct flowside side;
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flowside_from_af(&side, af, eaddr, eport, faddr, fport);
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return flowside_lookup(c, proto, pif, &side);
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}
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/**
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* flow_defer_handler() - Handler for per-flow deferred and timed tasks
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* @c: Execution context
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@ -543,7 +683,12 @@ void flow_defer_handler(const struct ctx *c, const struct timespec *now)
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*/
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void flow_init(void)
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{
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unsigned b;
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/* Initial state is a single free cluster containing the whole table */
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flowtab[0].free.n = FLOW_MAX;
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flowtab[0].free.next = FLOW_MAX;
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for (b = 0; b < FLOW_HASH_SIZE; b++)
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flow_hashtab[b] = FLOW_SIDX_NONE;
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}
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