In a later patch, the bpf prog only wants to be called to handle
a header option if that particular header option cannot be handled by
the kernel. This unknown option could be written by the peer's bpf-prog.
It could also be a new standard option that the running kernel does not
support it while a bpf-prog can handle it.
This patch adds a "saw_unknown" bit to "struct tcp_options_received"
and it uses an existing one byte hole to do that. "saw_unknown" will
be set in tcp_parse_options() if it sees an option that the kernel
cannot handle.
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
include/linux/tcp.h | 2 ++
net/ipv4/tcp_input.c | 22 ++++++++++++++++------
2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 2088d5a079af..29d166263ae7 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -92,6 +92,8 @@ struct tcp_options_received {
smc_ok : 1, /* SMC seen on SYN packet */
snd_wscale : 4, /* Window scaling received from sender */
rcv_wscale : 4; /* Window scaling to send to receiver */
+ u8 saw_unknown:1, /* Received unknown option */
+ unused:7;
u8 num_sacks; /* Number of SACK blocks */
u16 user_mss; /* mss requested by user in ioctl */
u16 mss_clamp; /* Maximal mss, negotiated at connection setup */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4aaedcf71973..9072d9160df9 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3801,7 +3801,7 @@ static void tcp_parse_fastopen_option(int len, const unsigned char *cookie,
foc->exp = exp_opt;
}
-static void smc_parse_options(const struct tcphdr *th,
+static bool smc_parse_options(const struct tcphdr *th,
struct tcp_options_received *opt_rx,
const unsigned char *ptr,
int opsize)
@@ -3810,10 +3810,13 @@ static void smc_parse_options(const struct tcphdr *th,
if (static_branch_unlikely(&tcp_have_smc)) {
if (th->syn && !(opsize & 1) &&
opsize >= TCPOLEN_EXP_SMC_BASE &&
- get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC)
+ get_unaligned_be32(ptr) == TCPOPT_SMC_MAGIC) {
opt_rx->smc_ok = 1;
+ return true;
+ }
}
#endif
+ return false;
}
/* Try to parse the MSS option from the TCP header. Return 0 on failure, clamped
@@ -3874,6 +3877,7 @@ void tcp_parse_options(const struct net *net,
ptr = (const unsigned char *)(th + 1);
opt_rx->saw_tstamp = 0;
+ opt_rx->saw_unknown = 0;
while (length > 0) {
int opcode = *ptr++;
@@ -3964,15 +3968,21 @@ void tcp_parse_options(const struct net *net,
*/
if (opsize >= TCPOLEN_EXP_FASTOPEN_BASE &&
get_unaligned_be16(ptr) ==
- TCPOPT_FASTOPEN_MAGIC)
+ TCPOPT_FASTOPEN_MAGIC) {
tcp_parse_fastopen_option(opsize -
TCPOLEN_EXP_FASTOPEN_BASE,
ptr + 2, th->syn, foc, true);
- else
- smc_parse_options(th, opt_rx, ptr,
- opsize);
+ break;
+ }
+
+ if (smc_parse_options(th, opt_rx, ptr, opsize))
+ break;
+
+ opt_rx->saw_unknown = 1;
break;
+ default:
+ opt_rx->saw_unknown = 1;
}
ptr += opsize-2;
length -= opsize;
--
2.24.1
