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tcp: Add saw_unknown to struct tcp_options_received 

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.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200820190033.2884430-1-kafai@fb.com
This commit is contained in:
Martin KaFai Lau 2020-08-20 12:00:33 -07:00 committed by Alexei Starovoitov
parent ca584ba070
commit 7656d68455
2 changed files with 18 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/tcp.h
View File

@ -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 */

22
net/ipv4/tcp_input.c
View File

@ -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;