[RFC PATCH v2 13/21] net/tcp: Pad TCP options out to a fixed size for netgpu
From: Jonathan Lemon <hidden>
Date: 2020-07-27 22:45:14
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Jonathan Lemon <redacted> The "header splitting" feature used by netgpu doesn't actually parse the incoming packet header. Instead, it splits the packet at a fixed offset. In order for this to work, the sender needs to send packets with a fixed header size. Signed-off-by: Jonathan Lemon <redacted> --- net/ipv4/tcp_output.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index d8f16f6a9b02..e8a74d0f7ad2 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c@@ -438,6 +438,7 @@ struct tcp_out_options { u8 ws; /* window scale, 0 to disable */ u8 num_sack_blocks; /* number of SACK blocks to include */ u8 hash_size; /* bytes in hash_location */ + u8 pad_size; /* additional nops for padding */ __u8 *hash_location; /* temporary pointer, overloaded */ __u32 tsval, tsecr; /* need to include OPTION_TS */ struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */
@@ -562,6 +563,17 @@ static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, smc_options_write(ptr, &options); mptcp_options_write(ptr, opts); + +#if IS_ENABLED(CONFIG_NETGPU) + /* pad out options */ + if (opts->pad_size) { + int len = opts->pad_size; + u8 *p = (u8 *)ptr; + + while (len--) + *p++ = TCPOPT_NOP; + } +#endif } static void smc_set_option(const struct tcp_sock *tp,
@@ -826,6 +838,14 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; } +#if IS_ENABLED(CONFIG_NETGPU) + /* force padding */ + if (size < 20) { + opts->pad_size = 20 - size; + size += opts->pad_size; + } +#endif + return size; }
--
2.24.1