On 4/22/25 5:35 PM, chia-yu.chang@nokia-bell-labs.com wrote:
@@ -709,6 +709,8 @@ static __be32 *process_tcp_ao_options(struct tcp_sock *tp, return ptr; } +#define NOP_LEFTOVER ((TCPOPT_NOP << 8) | TCPOPT_NOP)
/* Write previously computed TCP options to the packet.
- Beware: Something in the Internet is very sensitive to the ordering of
@@ -727,8 +729,10 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, struct tcp_out_options *opts, struct tcp_key *key) {
- u16 leftover_bytes = NOP_LEFTOVER; /* replace next NOPs if avail */ __be32 *ptr = (__be32 *)(th + 1); u16 options = opts->options; /* mungable copy */
- int leftover_size = 2;
if (tcp_key_is_md5(key)) { *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | @@ -763,17 +767,22 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, } if (unlikely(OPTION_SACK_ADVERTISE & options)) {
*ptr++ = htonl((TCPOPT_NOP << 24) |(TCPOPT_NOP << 16) |
*ptr++ = htonl((leftover_bytes << 16) | (TCPOPT_SACK_PERM << 8) | TCPOLEN_SACK_PERM);leftover_bytes = NOP_LEFTOVER;
Why? isn't leftover_bytes already == NOP_LEFTOVER?
} if (unlikely(OPTION_WSCALE & options)) {
*ptr++ = htonl((TCPOPT_NOP << 24) |
u8 highbyte = TCPOPT_NOP;if (unlikely(leftover_size == 1))
How can the above conditional be true?
highbyte = leftover_bytes >> 8;*ptr++ = htonl((highbyte << 24) | (TCPOPT_WINDOW << 16) | (TCPOLEN_WINDOW << 8) | opts->ws);leftover_bytes = NOP_LEFTOVER;
Why? isn't leftover_bytes already == NOP_LEFTOVER?
} if (unlikely(opts->num_sack_blocks)) { @@ -781,8 +790,7 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, tp->duplicate_sack : tp->selective_acks; int this_sack;
*ptr++ = htonl((TCPOPT_NOP << 24) |(TCPOPT_NOP << 16) |
*ptr++ = htonl((leftover_bytes << 16) | (TCPOPT_SACK << 8) | (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK)));@@ -794,6 +802,10 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp, } tp->rx_opt.dsack = 0;
- } else if (unlikely(leftover_bytes != NOP_LEFTOVER)) {
I really feel like I'm missing some code chunk, but I don't see any possible value for leftover_bytes other than NOP_LEFTOVER
/P