TCP keepalives aren't technically a flag, but they are a zero-data segment so they can be generated with only a small modification to tcp_{buf,vu}_send_flag(). Implement this, using a new "pseudo-flag" value (similar to DUP_ACK), KEEPALIVE. Signed-off-by: David Gibson --- tcp_buf.c | 4 ++++ tcp_internal.h | 2 ++ tcp_vu.c | 3 +++ 3 files changed, 9 insertions(+) diff --git a/tcp_buf.c b/tcp_buf.c index d2925410..18bdce81 100644 --- a/tcp_buf.c +++ b/tcp_buf.c @@ -227,6 +227,10 @@ int tcp_buf_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) tcp_frame_conns[tcp_payload_used++] = conn; l4len = optlen + sizeof(struct tcphdr); iov[TCP_IOV_PAYLOAD].iov_len = l4len; + + if (flags & KEEPALIVE) + seq--; + tcp_l2_buf_fill_headers(c, conn, iov, NULL, seq, false); tcp_l2_buf_pad(iov); diff --git a/tcp_internal.h b/tcp_internal.h index 5f8fb358..36f443b4 100644 --- a/tcp_internal.h +++ b/tcp_internal.h @@ -38,6 +38,8 @@ /* Flags for internal usage */ #define DUP_ACK (1 << 5) +#define KEEPALIVE (1 << 6) + #define OPT_EOL 0 #define OPT_NOP 1 #define OPT_MSS 2 diff --git a/tcp_vu.c b/tcp_vu.c index b9e9b55e..f2d38aa5 100644 --- a/tcp_vu.c +++ b/tcp_vu.c @@ -135,6 +135,9 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags) flags_elem[0].in_sg[0].iov_len = hdrlen + optlen; payload = IOV_TAIL(flags_elem[0].in_sg, 1, hdrlen); + if (flags & KEEPALIVE) + seq--; + tcp_fill_headers(c, conn, NULL, eh, ip4h, ip6h, th, &payload, NULL, seq, !*c->pcap); -- 2.52.0