http://bugs.winehq.org/show_bug.cgi?id=60508 Bug ID: 60508 Summary: winsock: TCP SYN MSS and Window Scale negotiation discrepancy under Linux host cellular interfaces Product: Wine Version: 10.0 Hardware: x86-64 OS: Linux Status: UNCONFIRMED Severity: normal Priority: P2 Component: winsock Assignee: wine-bugs@list.winehq.org Reporter: info@neurobitlab.com Target Milestone: --- Distribution: --- When executing Windows anti-detect browsers and multi-profile scraping runners (such as AdsPower SunBrowser, GoLogin, or automated Chromium forks) inside Wine on Linux, socket connections initiated through Winsock (WSASocketW / connect) fail to properly inherit or reflect host TCP option parameters when bound to cellular interfaces (4G/5G USB modems with Carrier-Grade NAT). In standard Windows kernel network stacks, the TCP handshake SYN packet contains specific option orderings (MSS, Window Scale, SACK Permitted, Timestamps) defined by IETF RFC 7323 (https://datatracker.ietf.org/doc/html/rfc7323) and standard TCP semantics in RFC 9293 (https://datatracker.ietf.org/doc/html/rfc9293). When Windows applications run under Wine, Winsock delegates directly to the host Linux kernel socket layer. On mobile broadband links subject to GTP-U encapsulation and RFC 6598 carrier NAT, this creates passive OS fingerprint mismatches where upstream WAFs (Cloudflare, DataDome) detect Linux TCP SYN signatures despite the application advertising Windows HTTP headers: https://pxm2.io/blog/post/the-synergy-between-adspower-and-4g5g-mobile-proxi... Steps to reproduce: 1. Run a 64-bit Windows Chromium / AdsPower instance under Wine 9.x/10.0 on Linux. 2. Route egress traffic through a local SOCKS5 proxy connected to an LTE/5G USB interface (e.g. Quectel EC25 / RM500Q). 3. Capture the outgoing TCP SYN packet on the egress interface using tcpdump: tcpdump -nn -i wwan0 "tcp[tcpflags] & (tcp-syn) != 0" -c 1 -vvv 4. Notice that Winsock does not allow setting custom TCP_MAXSEG or TCP window scaling flags via setsockopt(), leading to an identifiable discrepancy between the guest Windows user-agent profile and the host Linux SYN packet layout. Expected behavior: Winsock should provide a mechanism or configuration option (or honor socket-level options) to align TCP options negotiation with standard Windows socket behavior. -- Do not reply to this email, post in Bugzilla using the above URL to reply. You are receiving this mail because: You are watching all bug changes.