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flow, tcp: Generalise TCP hash table to general flow hash table

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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 2024-07-18 15:26:35 +10:00 • committed by Stefano Brivio
parent 163a339214
commit acca4235c4
5 changed files with 172 additions and 145 deletions

147
tcp.c
View file

@ -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);