From acca4235c46f0b2ecceb991d75a09616309afb3c Mon Sep 17 00:00:00 2001 From: David Gibson Date: Thu, 18 Jul 2024 15:26:35 +1000 Subject: 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 Signed-off-by: Stefano Brivio --- flow.c | 155 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-- flow.h | 11 ++-- flow_table.h | 3 -- tcp.c | 147 ++++++------------------------------------------------ tcp_internal.h | 1 + 5 files changed, 172 insertions(+), 145 deletions(-) diff --git a/flow.c b/flow.c index e70e3cb..b291f25 100644 --- a/flow.c +++ b/flow.c @@ -105,6 +105,16 @@ unsigned flow_first_free; union flow flowtab[FLOW_MAX]; static const union flow *flow_new_entry; /* = NULL */ +/* Hash table to index it */ +#define FLOW_HASH_LOAD 70 /* % */ +#define FLOW_HASH_SIZE ((2 * FLOW_MAX * 100 / FLOW_HASH_LOAD)) + +/* Table for lookup from flowside information */ +static flow_sidx_t flow_hashtab[FLOW_HASH_SIZE]; + +static_assert(ARRAY_SIZE(flow_hashtab) >= 2 * FLOW_MAX, +"Safe linear probing requires hash table with more entries than the number of sides in the flow table"); + /* Last time the flow timers ran */ static struct timespec flow_timer_run; @@ -116,9 +126,9 @@ static struct timespec flow_timer_run; * @faddr: Forwarding address (pointer to in_addr or in6_addr) * @fport: Forwarding port */ -void flowside_from_af(struct flowside *side, sa_family_t af, - const void *eaddr, in_port_t eport, - const void *faddr, in_port_t fport) +static void flowside_from_af(struct flowside *side, sa_family_t af, + const void *eaddr, in_port_t eport, + const void *faddr, in_port_t fport) { if (faddr) inany_from_af(&side->faddr, af, faddr); @@ -410,8 +420,8 @@ void flow_alloc_cancel(union flow *flow) * * Return: hash value */ -uint64_t flow_hash(const struct ctx *c, uint8_t proto, uint8_t pif, - const struct flowside *side) +static uint64_t flow_hash(const struct ctx *c, uint8_t proto, uint8_t pif, + const struct flowside *side) { struct siphash_state state = SIPHASH_INIT(c->hash_secret); @@ -430,6 +440,136 @@ uint64_t flow_hash(const struct ctx *c, uint8_t proto, uint8_t pif, (uint64_t)side->eport); } +/** + * flow_sidx_hash() - Calculate hash value for given side of a given flow + * @c: Execution context + * @sidx: Flow & side index to get hash for + * + * Return: hash value, of the flow & side represented by @sidx + */ +static uint64_t flow_sidx_hash(const struct ctx *c, flow_sidx_t sidx) +{ + const struct flow_common *f = &flow_at_sidx(sidx)->f; + return flow_hash(c, FLOW_PROTO(f), + f->pif[sidx.sidei], &f->side[sidx.sidei]); +} + +/** + * flow_hash_probe() - Find hash bucket for a flow + * @c: Execution context + * @sidx: Flow and side to find bucket for + * + * Return: If @sidx is in the hash table, its current bucket, otherwise a + * suitable free bucket for it. + */ +static inline unsigned flow_hash_probe(const struct ctx *c, flow_sidx_t sidx) +{ + unsigned b = flow_sidx_hash(c, sidx) % FLOW_HASH_SIZE; + + /* Linear probing */ + while (flow_sidx_valid(flow_hashtab[b]) && + !flow_sidx_eq(flow_hashtab[b], sidx)) + b = mod_sub(b, 1, FLOW_HASH_SIZE); + + return b; +} + +/** + * flow_hash_insert() - Insert side of a flow into into hash table + * @c: Execution context + * @sidx: Flow & side index + */ +void flow_hash_insert(const struct ctx *c, flow_sidx_t sidx) +{ + unsigned b = flow_hash_probe(c, sidx); + + flow_hashtab[b] = sidx; + flow_dbg(flow_at_sidx(sidx), "Side %u hash table insert: bucket: %u", + sidx.sidei, b); +} + +/** + * flow_hash_remove() - Drop side of a flow from the hash table + * @c: Execution context + * @sidx: Side of flow to remove + */ +void flow_hash_remove(const struct ctx *c, flow_sidx_t sidx) +{ + unsigned b = flow_hash_probe(c, sidx), s; + + if (!flow_sidx_valid(flow_hashtab[b])) + return; /* Redundant remove */ + + flow_dbg(flow_at_sidx(sidx), "Side %u hash table remove: bucket: %u", + sidx.sidei, b); + + /* Scan the remainder of the cluster */ + for (s = mod_sub(b, 1, FLOW_HASH_SIZE); + flow_sidx_valid(flow_hashtab[s]); + s = mod_sub(s, 1, FLOW_HASH_SIZE)) { + unsigned h = flow_sidx_hash(c, flow_hashtab[s]) % FLOW_HASH_SIZE; + + if (!mod_between(h, s, b, FLOW_HASH_SIZE)) { + /* flow_hashtab[s] can live in flow_hashtab[b]'s slot */ + debug("hash table remove: shuffle %u -> %u", s, b); + flow_hashtab[b] = flow_hashtab[s]; + b = s; + } + } + + flow_hashtab[b] = FLOW_SIDX_NONE; +} + +/** + * flowside_lookup() - Look for a matching flowside in the flow table + * @c: Execution context + * @proto: Protocol of the flow (IP L4 protocol number) + * @pif: pif to look for in the table + * @side: Flowside to look for in the table + * + * Return: sidx of the matching flow & side, FLOW_SIDX_NONE if not found + */ +static flow_sidx_t flowside_lookup(const struct ctx *c, uint8_t proto, + uint8_t pif, const struct flowside *side) +{ + flow_sidx_t sidx; + union flow *flow; + unsigned b; + + b = flow_hash(c, proto, pif, side) % FLOW_HASH_SIZE; + while ((sidx = flow_hashtab[b], flow = flow_at_sidx(sidx)) && + !(FLOW_PROTO(&flow->f) == proto && + flow->f.pif[sidx.sidei] == pif && + flowside_eq(&flow->f.side[sidx.sidei], side))) + b = (b + 1) % FLOW_HASH_SIZE; + + return flow_hashtab[b]; +} + +/** + * flow_lookup_af() - Look up a flow given addressing information + * @c: Execution context + * @proto: Protocol of the flow (IP L4 protocol number) + * @pif: Interface of the flow + * @af: Address family, AF_INET or AF_INET6 + * @eaddr: Guest side endpoint address (guest local address) + * @faddr: Guest side forwarding address (guest remote address) + * @eport: Guest side endpoint port (guest local port) + * @fport: Guest side forwarding port (guest remote port) + * + * Return: sidx of the matching flow & side, FLOW_SIDX_NONE if not found + */ +flow_sidx_t flow_lookup_af(const struct ctx *c, + uint8_t proto, uint8_t pif, sa_family_t af, + const void *eaddr, const void *faddr, + in_port_t eport, in_port_t fport) +{ + struct flowside side; + + flowside_from_af(&side, af, eaddr, eport, faddr, fport); + return flowside_lookup(c, proto, pif, &side); +} + /** * flow_defer_handler() - Handler for per-flow deferred and timed tasks * @c: Execution context @@ -543,7 +683,12 @@ void flow_defer_handler(const struct ctx *c, const struct timespec *now) */ void flow_init(void) { + unsigned b; + /* Initial state is a single free cluster containing the whole table */ flowtab[0].free.n = FLOW_MAX; flowtab[0].free.next = FLOW_MAX; + + for (b = 0; b < FLOW_HASH_SIZE; b++) + flow_hashtab[b] = FLOW_SIDX_NONE; } diff --git a/flow.h b/flow.h index a0550dc..fcb4121 100644 --- a/flow.h +++ b/flow.h @@ -164,10 +164,6 @@ static inline bool flowside_eq(const struct flowside *left, left->fport == right->fport; } -void flowside_from_af(struct flowside *side, sa_family_t af, - const void *eaddr, in_port_t eport, - const void *faddr, in_port_t fport); - /** * struct flow_common - Common fields for packet flows * @state: State of the flow table entry @@ -233,6 +229,13 @@ static inline bool flow_sidx_eq(flow_sidx_t a, flow_sidx_t b) return (a.flowi == b.flowi) && (a.sidei == b.sidei); } +void flow_hash_insert(const struct ctx *c, flow_sidx_t sidx); +void flow_hash_remove(const struct ctx *c, flow_sidx_t sidx); +flow_sidx_t flow_lookup_af(const struct ctx *c, + uint8_t proto, uint8_t pif, sa_family_t af, + const void *eaddr, const void *faddr, + in_port_t eport, in_port_t fport); + union flow; void flow_init(void); diff --git a/flow_table.h b/flow_table.h index b3cb546..aabdbb7 100644 --- a/flow_table.h +++ b/flow_table.h @@ -146,7 +146,4 @@ void flow_activate(struct flow_common *f); #define FLOW_ACTIVATE(flow_) \ (flow_activate(&(flow_)->f)) -uint64_t flow_hash(const struct ctx *c, uint8_t proto, uint8_t pif, - const struct flowside *side); - #endif /* FLOW_TABLE_H */ diff --git a/tcp.c b/tcp.c index 5c8c8d1..0964855 100644 --- a/tcp.c +++ b/tcp.c @@ -305,9 +305,6 @@ #include "tcp_internal.h" #include "tcp_buf.h" -#define TCP_HASH_TABLE_LOAD 70 /* % */ -#define TCP_HASH_TABLE_SIZE (FLOW_MAX * 100 / TCP_HASH_TABLE_LOAD) - /* MSS rounding: see SET_MSS() */ #define MSS_DEFAULT 536 #define WINDOW_DEFAULT 14600 /* RFC 6928 */ @@ -377,12 +374,6 @@ bool peek_offset_cap; /* sendmsg() to socket */ static struct iovec tcp_iov [UIO_MAXIOV]; -/* Table for lookup from flowside information */ -static flow_sidx_t tc_hash[TCP_HASH_TABLE_SIZE]; - -static_assert(ARRAY_SIZE(tc_hash) >= FLOW_MAX, - "Safe linear probing requires hash table larger than connection table"); - /* Pools for pre-opened sockets (in init) */ int init_sock_pool4 [TCP_SOCK_POOL_SIZE]; int init_sock_pool6 [TCP_SOCK_POOL_SIZE]; @@ -605,9 +596,6 @@ void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn, tcp_timer_ctl(c, conn); } -static void tcp_hash_remove(const struct ctx *c, - const struct tcp_tap_conn *conn); - /** * conn_event_do() - Set and log connection events, update epoll state * @c: Execution context @@ -653,7 +641,7 @@ void conn_event_do(const struct ctx *c, struct tcp_tap_conn *conn, num == -1 ? "CLOSED" : tcp_event_str[num]); if (event == CLOSED) - tcp_hash_remove(c, conn); + flow_hash_remove(c, TAP_SIDX(conn)); else if ((event == TAP_FIN_RCVD) && !(conn->events & SOCK_FIN_RCVD)) conn_flag(c, conn, ACTIVE_CLOSE); else @@ -852,117 +840,6 @@ static int tcp_opt_get(const char *opts, size_t len, uint8_t type_find, return -1; } -/** - * tcp_conn_hash() - Calculate hash bucket of an existing connection - * @c: Execution context - * @conn: Connection - * - * Return: hash value, needs to be adjusted for table size - */ -static uint64_t tcp_conn_hash(const struct ctx *c, - const struct tcp_tap_conn *conn) -{ - const struct flowside *tapside = TAPFLOW(conn); - - return flow_hash(c, IPPROTO_TCP, conn->f.pif[TAPSIDE(conn)], tapside); -} - -/** - * tcp_hash_probe() - Find hash bucket for a connection - * @c: Execution context - * @conn: Connection to find bucket for - * - * Return: If @conn is in the table, its current bucket, otherwise a suitable - * free bucket for it. - */ -static inline unsigned tcp_hash_probe(const struct ctx *c, - const struct tcp_tap_conn *conn) -{ - unsigned b = tcp_conn_hash(c, conn) % TCP_HASH_TABLE_SIZE; - flow_sidx_t sidx = FLOW_SIDX(conn, TAPSIDE(conn)); - - /* Linear probing */ - while (flow_sidx_valid(tc_hash[b]) && !flow_sidx_eq(tc_hash[b], sidx)) - b = mod_sub(b, 1, TCP_HASH_TABLE_SIZE); - - return b; -} - -/** - * tcp_hash_insert() - Insert connection into hash table, chain link - * @c: Execution context - * @conn: Connection pointer - */ -static void tcp_hash_insert(const struct ctx *c, struct tcp_tap_conn *conn) -{ - unsigned b = tcp_hash_probe(c, conn); - - tc_hash[b] = FLOW_SIDX(conn, TAPSIDE(conn)); - flow_dbg(conn, "hash table insert: sock %i, bucket: %u", conn->sock, b); -} - -/** - * tcp_hash_remove() - Drop connection from hash table, chain unlink - * @c: Execution context - * @conn: Connection pointer - */ -static void tcp_hash_remove(const struct ctx *c, - const struct tcp_tap_conn *conn) -{ - unsigned b = tcp_hash_probe(c, conn), s; - union flow *flow; - - if (!flow_sidx_valid(tc_hash[b])) - return; /* Redundant remove */ - - flow_dbg(conn, "hash table remove: sock %i, bucket: %u", conn->sock, b); - - /* Scan the remainder of the cluster */ - for (s = mod_sub(b, 1, TCP_HASH_TABLE_SIZE); - (flow = flow_at_sidx(tc_hash[s])); - s = mod_sub(s, 1, TCP_HASH_TABLE_SIZE)) { - unsigned h = tcp_conn_hash(c, &flow->tcp) % TCP_HASH_TABLE_SIZE; - - if (!mod_between(h, s, b, TCP_HASH_TABLE_SIZE)) { - /* tc_hash[s] can live in tc_hash[b]'s slot */ - debug("hash table remove: shuffle %u -> %u", s, b); - tc_hash[b] = tc_hash[s]; - b = s; - } - } - - tc_hash[b] = FLOW_SIDX_NONE; -} - -/** - * tcp_hash_lookup() - Look up connection given remote address and ports - * @c: Execution context - * @af: Address family, AF_INET or AF_INET6 - * @eaddr: Guest side endpoint address (guest local address) - * @faddr: Guest side forwarding address (guest remote address) - * @eport: Guest side endpoint port (guest local port) - * @fport: Guest side forwarding port (guest remote port) - * - * Return: connection pointer, if found, -ENOENT otherwise - */ -static struct tcp_tap_conn *tcp_hash_lookup(const struct ctx *c, sa_family_t af, - const void *eaddr, const void *faddr, - in_port_t eport, in_port_t fport) -{ - struct flowside side; - union flow *flow; - unsigned b; - - flowside_from_af(&side, af, eaddr, eport, faddr, fport); - - b = flow_hash(c, IPPROTO_TCP, PIF_TAP, &side) % TCP_HASH_TABLE_SIZE; - while ((flow = flow_at_sidx(tc_hash[b])) && - !flowside_eq(&flow->f.side[TAPSIDE(flow)], &side)) - b = mod_sub(b, 1, TCP_HASH_TABLE_SIZE); - - return &flow->tcp; -} - /** * tcp_flow_defer() - Deferred per-flow handling (clean up closed connections) * @conn: Connection to handle @@ -1710,7 +1587,7 @@ static void tcp_conn_from_tap(struct ctx *c, sa_family_t af, tcp_seq_init(c, conn, now); conn->seq_ack_from_tap = conn->seq_to_tap; - tcp_hash_insert(c, conn); + flow_hash_insert(c, TAP_SIDX(conn)); tcp_bind_outbound(c, conn, s); @@ -2047,6 +1924,8 @@ int tcp_tap_handler(struct ctx *c, uint8_t pif, sa_family_t af, const struct tcphdr *th; size_t optlen, len; const char *opts; + union flow *flow; + flow_sidx_t sidx; int ack_due = 0; int count; @@ -2062,17 +1941,22 @@ int tcp_tap_handler(struct ctx *c, uint8_t pif, sa_family_t af, optlen = MIN(optlen, ((1UL << 4) /* from doff width */ - 6) * 4UL); opts = packet_get(p, idx, sizeof(*th), optlen, NULL); - conn = tcp_hash_lookup(c, af, saddr, daddr, - ntohs(th->source), ntohs(th->dest)); + sidx = flow_lookup_af(c, IPPROTO_TCP, PIF_TAP, af, saddr, daddr, + ntohs(th->source), ntohs(th->dest)); + flow = flow_at_sidx(sidx); /* New connection from tap */ - if (!conn) { + if (!flow) { if (opts && th->syn && !th->ack) tcp_conn_from_tap(c, af, saddr, daddr, th, opts, optlen, now); return 1; } + ASSERT(flow->f.type == FLOW_TCP); + ASSERT(pif_at_sidx(sidx) == PIF_TAP); + conn = &flow->tcp; + flow_trace(conn, "packet length %zu from tap", len); if (th->rst) { @@ -2250,7 +2134,7 @@ static void tcp_tap_conn_from_sock(struct ctx *c, in_port_t dstport, conn_event(c, conn, SOCK_ACCEPTED); tcp_seq_init(c, conn, now); - tcp_hash_insert(c, conn); + flow_hash_insert(c, TAP_SIDX(conn)); conn->seq_ack_from_tap = conn->seq_to_tap; @@ -2652,14 +2536,11 @@ static void tcp_sock_refill_init(const struct ctx *c) */ int tcp_init(struct ctx *c) { - unsigned int b, optv = 0; + unsigned int optv = 0; int s; ASSERT(!c->no_tcp); - for (b = 0; b < TCP_HASH_TABLE_SIZE; b++) - tc_hash[b] = FLOW_SIDX_NONE; - if (c->ifi4) tcp_sock4_iov_init(c); diff --git a/tcp_internal.h b/tcp_internal.h index ac6d4b2..8b60aab 100644 --- a/tcp_internal.h +++ b/tcp_internal.h @@ -42,6 +42,7 @@ #define TAPSIDE(conn_) ((conn_)->f.pif[1] == PIF_TAP) #define TAPFLOW(conn_) (&((conn_)->f.side[TAPSIDE(conn_)])) +#define TAP_SIDX(conn_) (FLOW_SIDX((conn_), TAPSIDE(conn_))) #define CONN_V4(conn) (!!inany_v4(&TAPFLOW(conn)->faddr)) #define CONN_V6(conn) (!CONN_V4(conn)) -- cgit v1.2.3