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flow: Add flow_sidx_valid() helper

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To implement the TCP hash table, we need an invalid (NULL-like) value for
flow_sidx_t.  We use FLOW_SIDX_NONE for that, but for defensiveness, we
treat (usually) anything with an out of bounds flow index the same way.

That's not always done consistently though.  In flow_at_sidx() we open code
a check on the flow index.  In tcp_hash_probe() we instead compare against
FLOW_SIDX_NONE, and in some other places we use the fact that
flow_at_sidx() will return NULL in this case, even if we don't otherwise
need the flow it returns.

Clean this up a bit, by adding an explicit flow_sidx_valid() test function.

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 2024-07-05 20:44:00 +10:00 committed by Stefano Brivio
parent 74c1c5efcf
commit 8f8eb73482
3 changed files with 15 additions and 5 deletions
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11
flow.h
View File

@ -176,6 +176,17 @@ static_assert(sizeof(flow_sidx_t) <= sizeof(uint32_t),
#define FLOW_SIDX_NONE ((flow_sidx_t){ .flow = FLOW_MAX })
/**
* flow_sidx_valid() - Test if a sidx is valid
* @sidx: sidx value
*
* Return: true if @sidx refers to a valid flow & side
*/
static inline bool flow_sidx_valid(flow_sidx_t sidx)
{
return sidx.flow < FLOW_MAX;
}
/**
* flow_sidx_eq() - Test if two sidx values are equal
* @a, @b: sidx values

2
flow_table.h
View File

@ -73,7 +73,7 @@ static inline unsigned flow_idx(const struct flow_common *f)
*/
static inline union flow *flow_at_sidx(flow_sidx_t sidx)
{
if (sidx.flow >= FLOW_MAX)
if (!flow_sidx_valid(sidx))
return NULL;
return FLOW(sidx.flow);
}

7
tcp.c
View File

@ -880,8 +880,7 @@ static inline unsigned tcp_hash_probe(const struct ctx *c,
flow_sidx_t sidx = FLOW_SIDX(conn, TAPSIDE(conn));
/* Linear probing */
while (!flow_sidx_eq(tc_hash[b], FLOW_SIDX_NONE) &&
!flow_sidx_eq(tc_hash[b], sidx))
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;
@ -909,9 +908,9 @@ 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 = flow_at_sidx(tc_hash[b]);
union flow *flow;
if (!flow)
if (!flow_sidx_valid(tc_hash[b]))
return; /* Redundant remove */
flow_dbg(conn, "hash table remove: sock %i, bucket: %u", conn->sock, b);