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tcp: Add connection union type

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Currently, the tables for spliced and non-spliced connections are entirely
separate, with different types in different arrays.  We want to unify them.
As a first step, create a union type which can represent either a spliced
or non-spliced connection.  For them to be distinguishable, the individual
types need to have a common header added, with a bit indicating which type
this structure is.

This comes at the cost of increasing the size of tcp_tap_conn to over one
(64 byte) cacheline.  This isn't ideal, but it makes things simpler for now
and we'll re-optimize this later.

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 2022-11-17 16:58:44 +11:00 • committed by Stefano Brivio
parent 3cf027bd59
commit ff27fd63cd
3 changed files with 36 additions and 0 deletions

30
tcp_conn.h
View file

@ -11,8 +11,19 @@
#define TCP_HASH_BUCKET_BITS (TCP_CONN_INDEX_BITS + 1)
/**
* struct tcp_conn_common - Common fields for spliced and non-spliced
* @spliced: Is this a spliced connection?
*/
struct tcp_conn_common {
bool spliced :1;
};
extern const char *tcp_common_flag_str[];
/**
* struct tcp_tap_conn - Descriptor for a TCP connection (not spliced)
* @c: Fields common with tcp_splice_conn
* @next_index: Connection index of next item in hash chain, -1 for none
* @tap_mss: MSS advertised by tap/guest, rounded to 2 ^ TCP_MSS_BITS
* @sock: Socket descriptor number
@ -40,6 +51,9 @@
* @seq_init_from_tap: Initial sequence number from tap
*/
struct tcp_tap_conn {
/* Must be first element to match tcp_splice_conn */
struct tcp_conn_common c;
int next_index :TCP_CONN_INDEX_BITS + 2;
#define TCP_RETRANS_BITS 3
@ -122,6 +136,7 @@ struct tcp_tap_conn {
/**
* struct tcp_splice_conn - Descriptor for a spliced TCP connection
* @c: Fields common with tcp_tap_conn
* @a: File descriptor number of socket for accepted connection
* @pipe_a_b: Pipe ends for splice() from @a to @b
* @b: File descriptor number of peer connected socket
@ -134,6 +149,9 @@ struct tcp_tap_conn {
* @b_written: Bytes written to @b (not fully written from one @a read)
*/
struct tcp_splice_conn {
/* Must be first element to match tcp_tap_conn */
struct tcp_conn_common c;
int a;
int pipe_a_b[2];
int b;
@ -165,4 +183,16 @@ struct tcp_splice_conn {
uint32_t b_written;
};
/**
* union tcp_conn - Descriptor for a TCP connection (spliced or non-spliced)
* @c: Fields common between all variants
* @tap: Fields specific to non-spliced connections
* @splice: Fields specific to spliced connections
*/
union tcp_conn {
struct tcp_conn_common c;
struct tcp_tap_conn tap;
struct tcp_splice_conn splice;
};
#endif /* TCP_CONN_H */