On Thu, Feb 29, 2024 at 05:59:55PM +0100, Laurent
Vivier wrote:
Replace the macro SET_TCP_HEADER_COMMON_V4_V6()
by a new function
tcp_fill_header().
Move IPv4 and IPv6 code from tcp_l2_buf_fill_headers() to
tcp_fill_ipv4_header() and tcp_fill_ipv6_header()
Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
---
Notes:
v4:
- group all the ip6g initialisations together and
remove flow_lbl preset to 0
- add ASSERT(a4)
v3:
- add to sub-series part 1
v2:
- extract header filling functions from
"tcp: extract buffer management from tcp_send_flag()"
- rename them tcp_fill_flag_header()/tcp_fill_ipv4_header(),
tcp_fill_ipv6_header()
- use upside-down Christmas tree arguments order
- replace (void *) by (struct tcphdr *)
tcp.c | 154 +++++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 104 insertions(+), 50 deletions(-)
diff --git a/tcp.c b/tcp.c
index 5b2fdf662a6c..ced22534a103 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1326,6 +1326,108 @@ void tcp_defer_handler(struct ctx *c)
tcp_l2_data_buf_flush(c);
}
+/**
+ * tcp_fill_header() - Fill the TCP header fields for a given TCP segment.
+ *
+ * @th: Pointer to the TCP header structure
+ * @conn: Pointer to the TCP connection structure
+ * @seq: Sequence number
+ */
+static void tcp_fill_header(struct tcphdr *th,
+ const struct tcp_tap_conn *conn, uint32_t seq)
+{
+ th->source = htons(conn->fport);
+ th->dest = htons(conn->eport);
+ th->seq = htonl(seq);
+ th->ack_seq = htonl(conn->seq_ack_to_tap);
+ if (conn->events & ESTABLISHED) {
+ th->window = htons(conn->wnd_to_tap);
+ } else {
+ unsigned wnd = conn->wnd_to_tap << conn->ws_to_tap;
+
+ th->window = htons(MIN(wnd, USHRT_MAX));
+ }
+}
+
+/**
+ * tcp_fill_ipv4_header() - Fill 802.3, IPv4, TCP headers in pre-cooked buffers
I don't love the name, since it does also fill the TCP header. Maybe
'tcp_fill_headers4()'?
+ * @c: Execution context
+ * @conn: Connection pointer
+ * @iph: Pointer to IPv4 header, immediately followed by a TCP header
Again, really don't love accessing beyond a given pointer's type.
+ * @plen: Payload length (including TCP header
options)
+ * @check: Checksum, if already known
+ * @seq: Sequence number for this segment
+ *
+ * Return: IP frame length including L2 headers, host order
AFAICT the return value does *not* include the L2 headers..
+ */
+static size_t tcp_fill_ipv4_header(const struct ctx *c,
+ const struct tcp_tap_conn *conn,
+ struct iphdr *iph, size_t plen,
+ const uint16_t *check, uint32_t seq)
+{
+ size_t ip_len = plen + sizeof(struct iphdr) + sizeof(struct tcphdr);
+ const struct in_addr *a4 = inany_v4(&conn->faddr);
+ struct tcphdr *th = (struct tcphdr *)(iph + 1);
+
+ ASSERT(a4);
+
+ iph->tot_len = htons(ip_len);
+ iph->saddr = a4->s_addr;
+ iph->daddr = c->ip4.addr_seen.s_addr;
+
+ iph->check = check ? *check :
+ csum_ip4_header(iph->tot_len, IPPROTO_TCP,
+ iph->saddr, iph->daddr);
+
+
+ tcp_fill_header(th, conn, seq);
+
+ tcp_update_check_tcp4(iph);
It's a bit ugly that tcp_fill_header() fills the TCP header, but *not*
the checksum. Could we handle this by passing the pseudo-header psum
into tcp_fill_header()? Then the logic for that in
tcp_update_check_tcp4() would become part of this function.